Creamy, cheesy Zucchini Casserole will be your favorite zucchini side ever!

This Zucchini Casserole recipe is the ultimate zucchini side dish to enjoy the bounty of summer zucchini – even your kids will be begging you for seconds! Sliced zucchini is layered in a baking dish, drenched with cheesy cream sauce that has been simmered with herbs and then topped with bubbly golden Gruyere cheese and buttery, crispy panko. This zucchini casserole recipe tastes AMAZING enough for company and special occasions but is simple and easy enough to prepare any night of the week. It also happens to be low carb and can be made gluten free and keto if you skip the panko topping. Best of all, this zucchini casserole is not watery! I’m sharing my fool-proof techniques to prevent watery zucchini casserole so you get nothing but a decadent cocoon of cream sauce – and not a watery bath. This zucchini casserole is also make-ahead friendly and easy to customize the different cheeses, veggies and you can even add protein. In short, your search for the best zucchini casserole recipe stops here!

We love zucchini, especially in the summer months! Some of our favorite ways to serve zucchini are in zucchini lasagna, pasta primavera, summer Tuscan chicken skillet, and cilantro lime shrimp zucchini boats.

top view zucchini casserole made with heavy cream, cheese, sour cream and panko bread crumbs

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Zucchini Casserole Recipe

You’re going to love this easy zucchini casserole recipe! Even Patrick, after one bite, said, “Wow, that is SO good. I didn’t expect it to be that good.” And then he kept on eating and eating…

There are many ways to prepare zucchini casserole, but for this recipe I wanted the easiest AND the most delicious. Instead of pre-cooking the zucchini to get rid of moisture, laboriously shredding the zucchini or needing a mandoline to slice it super thin, I came up with a zucchini casserole that is deceptively simple to make but irresistibly delicious. It’s chock full of great flavor, texture, and of course, decadently creamy.

This zucchini casserole recipe is made with a full 3 pounds of zucchini drowned in a Gruyere, herb cream sauce that literally takes 3 minutes to make. Granted, you still need to salt the zucchini to remove excess moisture – but this is literally the “hardest” part, your hands-on prep is literally minutes. You can whip up the sauce while you wait for the zucchini to rest or prep your main dish, making this zucchini casserole a great one-pot side for a weeknight dinner.

Although, this simple side is SO good, you won’t want to keep it to ourselves. It’s perfect for entertaining and will convince even zucchini haters how much they love zucchini casserole – this zucchini casserole.

More reasons to love Zucchini casserole recipe:

CREAMY, NOT WATERY ZUCCHINI CASSEROLE: Many zucchini casserole recipes are disappointingly bland and watery– not this zucchini casserole. The sliced zucchini is first salted to draw out the moisture but the real game changer is the sauce. The rich, silky sauce starts out on the thicker side with the help of cornstarch, Gruyere and heavy cream and then thins to the perfect consistency as the zucchini bakes and releases moisture.
FLAVOR. The cream sauce simmers for three minutes with garlic, fresh or dried chives, parsley, thyme, oregano, onion powder, salt, pepper and a pinch of nutmeg. The aromatic herbs infuse the cream with flavor which in turn envelops the bed of zucchini with a blanket of creamy, satisfying aromatic herbs in every forkful.
EASY! Best of all, simmering requires no skill or effort! You simply toss all of the herbs and spices in with the cream and let them simmer while you wait for the salted zucchini slices to release their moisture. All that’s left to do is layer the zucchini and the sauce – easy peasy!
FLEXIBLE. You can make the zucchini casserole recipe as written or use it as a springboard for all sorts of variations – you can add squash, tomatoes, sausage, chicken, etc.
MAKE AHEAD. You will also love that this zucchini casserole reheats like a champ. Simply assemble up to day in advance and bake when ready.
LOW CARB. For those watching their carbs, this zucchini casserole is perfect. It’s low carb but still cozy, hearty and filling.
FAMILY SIZE. This zucchini casserole feeds the entire family and will leave everyone smiling for seconds.

up close of a scoop of zucchini casserole with bread crumbs

Zucchini Casserole Recipe Ingredients:

This zucchini casserole recipe uses just a handful of ingredients. You will need:

Zucchini: cut into 1/4-inch slices. When selecting zucchini, look for smaller, thicker veggies because they are more flavorful. The only downside of smaller zucchini is they don’t last as long so make sure to use them quickly.
Kosher salt: is used to draw out moisture from the zucchini. Do NOT use table salt. We need the larger grains of kosher salt because they sit on top of the zucchini and are much easier to wipe off verses table salt with can soak into the zucchini and make your zucchini casserole too salty.
Heavy Cream: is the base of the luxurious sauce. It is found in the refrigerated section near the milk at your grocery store and is usually labeled “heavy whipping cream.”
Cornstarch: helps thicken the sauce without having to make a roux so its beautifully rich and creamy and not runny.
Gruyere: is the consummate melting cheese and one of my favorite cheeses to use! It’s sweet, slightly salty, creamy, nutty and boasts enough flavor to cut through the richness of the sauce and melts seamlessly for additional luxurious creaminess. Gruyere is a Swiss cheese and can be found with the specialty cheese (usually by the deli) at your grocery store.
Mozzarella: is creamy, buttery and melts beautifully. Use only freshly grated mozzarella as pre-shredded cheeses are pumped with anti-clumping chemicals which prevents the cheese from melting as seamlessly.
Sour cream: helps thicken the sauce and adds a tangy richness.
Panko: is a Japanese breadcrumb sold in every grocery store (including Walmart) usually next to the other breadcrumbs. Panko breadcrumbs are larger and dryer than normal breadcrumbs so they absorb less moisture and become much crispier. Please do not substitute panko breadcrumbs with Italian breadcrumbs or you will be missing out on the gorgeous, satisfying CRUNCH.
Garlic: I use 2 cloves garlic but feel free to use less if you prefer. You may also use ½ teaspoon garlic powder – but the real stuff is so much better!
Chives: you can use fresh or dried chives, whatever you have on hand.
Seasonings: parsley, dried thyme, dried oregano, onion powder, salt, pepper and ground nutmeg infuse the velvety sauce with complex flavor while still allowing the zucchini to shine.

Ingredient Variations

Evaporated milk: if you’re trying to save some calories, you may substitute the heavy cream with evaporated milk. It won’t taste quite as decadent but still tasty.
Greek yogurt: you may substitute Greek yogurt for the sour cream but expect a slightly different flavor profile. Greek yogurt also won’t melt quite as seamlessly into the sauce but shouldn’t be noticeable once the zucchini casserole is baked.
Green onions: may be substituted for the chives.

IS THIS CASSEROLE GLUTEN FREE?

To make gluten free zucchini casserole, use your favorite gluten free panko or omit it altogether; the rest of the ingredients are gluten free.

HOW TO CHOOSE AND STORE ZUCCHINI

Appearance: look for zucchini that is dark green, plump, firm and smooth without blemishes, soft spots or shriveled skin.
Size: maturity is the biggest factor on flavor and texture so look for small to medium zucchini (which means they are young to middle-aged). These will be the most flavorful with tender, mildly sweet, flesh. Larger zucchini tends to be waterier, less flavorful and has larger seeds.
Weight: should feel heavy for its size.
How to store: zucchini is fairly deliciated and should be stored unwashed in a perforated or loosely closed plastic bag for 5-7 days. Don’t wash the zucchini until ready to use.
Should I peel zucchini? nope! Unlike cucumbers, zucchini skin is hardly noticeable and perfectly edible. It’s thin, soft, and contains healthy carotenoids.

side view of zucchini casserole recipe with a serving spoon showing how creamy it is

HOW THICK SHOULD THE ZUCCHINI SLICES BE?

Slice your zucchini 1/4-inch thick. This might be larger than you think, so I suggest measuring your first slice and matching the rest to it. We need thicker slices to stand up against the time it takes for the cheese to melt. The thicker zucchini slices remain al dente whereas thin slices will turn into mush while you wait for the cheese to melt and the sauce to bubble. Furthermore, it’s easier to add baking time once the cheese has melted if you want the zucchini more tender but you can’t undo mushy zucchini!

ZUCCHINI CASSEROLE VARIATIONS

This zucchini casserole is very flexible. You can play with different vegetables, different, proteins and a different sauce!

Swap vegetables: use half zucchini, half squash, or half zucchini, half eggplant. You may also add tomatoes but be aware they will make the casserole slightly watery.
Add protein: you can add protein such as Italian sausage, rotisserie chicken or even shrimp or lump crab meat. If you add protein, you will want to add extra sauce.
Add bacon: use thick cut bacon so it doesn’t get lost in the cheesiness. Stir half of the bacon into the sauce and sprinkle the rest on top.
Change sauce: mix up the flavor profile and swap the creamy sauce for Bolognese or marinara. In this case, I suggest swapping the Gruyere for Parmesan on the topping.
Swap cheeses: mix up the flavor profile by swapping the Gruyere for Gouda, Havarti, Asiago, Fontina, Muenster, brie, etc.
Switch up the herbs: you can add thyme, rosemary, marjoram, etc.
Add lemon: try adding a splash of lemon juice for a sunny pop of flavor.
Add Ins: you can layer the zucchini casserole with other ingredients such chopped sun-dried tomatoes, artichokes or roasted dried bell peppers. Take care to rinse and pat them very dry before chopping.
Change toppings: feel free to top your zucchini casserole with your favorite crunchy topping such as Ritz or omit it altogether. For Ritz, mix ¾ cup of crushed Ritz crackers with 3 tablespoons of melted butter.

THE KEY TO THE BEST ZUCCHINI CASSEROLE RECIPE

The key to the best zucchini casserole recipe is making sure that it’s luxuriously creamy and not disappointingly watery. Zucchini is 95% water so it is important to draw out the water from the zucchini before baking or the casserole will be a watery mess and result in a bland disappointment. Below I’ve detailed three tips to make zucchini casserole less watery that, when combined, work like a charm.

How to make zucchini casserole not watery:

Use small to medium zucchini. As previously discussed, smaller zucchini is less watery than large/mature zucchini.
Salt your zucchini and let it sit for 15 minutes. Spread the zucchini slices out into a single layer over several layers of paper towels. Sprinkle evenly with kosher salt and let rest 15 minutes. The salt draws out the moisture of the zucchini. After 15 minutes, you will notice pools of water on the surface of the zucchini. Brush the salt off with a wad of paper towels and pat dry. Make sure you use kosher salt and not table salt so it is easier to brush off.
Make the sauce thick. You will notice that the sauce is thicker than most -that is a good thing! If you start out with a thin sauce – it will only get thinner after the casserole is baked. To remedy this, we add cornstarch, sour cream and cheese directly to the sauce so its rich and creamy. While the zucchini casserole bakes, the sauce absorbs the extra liquid released by the zucchini (salting the zucchini releases a lot of the water but not all of it) so it thins to the perfect, silky, creamy, swaddling texture.

HOW TO MAKE ZUCCHINI CASSEROLE

Simmer cream sauce. While the zucchini slices are resting after being salted, make the herb cream by adding heavy cream, cornstarch, chives, garlic, dried parsley, dried thyme, dried oregano, onion powder, salt, pepper and nutmeg so a saucepan. Bring to a gentle simmer for 3 minutes, stirring often; it will be very thick.

Add cheese and sour cream. Reduce heat to low and add ½ cup Gruyere and stir until melted. Remove from heat and whisk in sour cream until smooth; set aside.

showing how to make zucchini casserole recipe with a collage of making cream sauce by adding Gruyere and sour cream

Assemble. Arrange half of the zucchini slices in the prepared baking dish. Evenly top with half of the herb cream (it will be thick). Top with remaining zucchini and remaining cream. Wiggle the dish so that the cream soaks in between the slices. Finally, top evenly with Gruyere and shredded mozzarella.

showing how to make zucchini casserole recipe with a collage showing how to layer zucchini, cream sauce and cheese and topping with pankoby

Bake. Cover the baking dish with foil and bake at 400 degrees for 30 minutes. After 30 minutes, remove baking dish from the oven. Remove the foil, top with panko and bake uncovered for an additional 5 minutes or until cheese is melted and bubbling and the zucchini is al tender crisp. Remove from oven and let stand 5 minutes before serving.

top view of zucchini casserole recipe with sour cream and bread crumbs

HOW TO MAKE THE CRISPIEST PANKO TOPPING

You can serve the zucchini casserole without the panko topping but I LOVE the contrasting crunch it adds so I don’t recommend skipping it. For lazy day panko, you can add it on top of the cheese before baking but for the CRUNCHIEST panko topping, I recommend toasting it in a skillet first – seriously culinary changing.

TO MAKE PANKO TOPPING:

1/2 cup panko breadcrumbs
1 tablespoon butter
1 tablespoon extra virgin olive oil

Melt butter in olive oil over medium heat in a medium skillet. Add panko and stir to coat. Continue cooking until crumbs become golden brown. Not only does this create the crunchiest panko ever but it becomes deliciously buttery AKA addicting!

TIPS AND TRICKS for the best zucchini casserole recipe:

Use small to medium zucchini for the best flavor, texture and less water output.
Cut zucchini into uniform thickness so they bake evenly.
Don’t slice zucchini less than 1/4-inch thick or it will become mushy by the time the cheese is melted and the sauce is bubbly. You can always add more baking time but you can’t undo mushy zucchini!
The zucchini MUST be salted and let to rest for 15 minutes to draw out excess water or your zucchini casserole will be watery.
Use kosher salt to salt the zucchini so it’s easier to wipe off and doesn’t penetrate the zucchini, otherwise your casserole will be salty.
Use freshly grated mozzarella as pre-grated cheeses use anti-clumping chemicals which prevents them from melting as well.
Add the Gruyere slowly in multiple batches – a handful at a time, stirring until completely melted, before adding some more.
The cream sauce will be thick which is a good thing! The sauce will absorb water released from the zucchini when baked to become the perfect consistency.
Simmer your “Herbed Cream” while your zucchini rests for maximum efficiency.
Test the zucchini for doneness in the CENTER to make sure they are tender-crisp.
Don’t overbake the zucchini casserole or it will become mushy. Cooking times will vary depending on multiple factors such has the shape/depth of your baking dish, actual zucchini thickness and the zucchini itself.
Garnish with fresh parsley or your favorite herbs for a fresh pop of color and flavor.

What to serve with this zucchini casserole?

This zucchini casserole goes with EVERYTHING! It’s fabulous in the summer months and it’s equally cozy in the winter months. Here are a few serving suggestions but don’t limit yourself to these alone!

Fantastic with any protein: fish, shrimp, steak, pork, chicken, etc.
Delicious with Italian food: Lasagna, Spaghetti, Chicken Parmesan, Baked Penne, Million Dollar Mac or Shrimp Fettuccine.
Cozy with classic comfort food: Beef Brisket, French Dips, Chicken Cordon Bleu, Oven Fried Chicken, Pot Roast, and BBQ Pork. s
Superb with company favorites: Spice Rubbed Steaks, Beef Tips and Gravy, Garlic Herb Butter Pork Tenderloin and Slow Cooker Honey Balsamic Roast Beef.

showing how to serve zucchini casserole with a serving spoon

HOW TO MAKE ZUCCHINI CASSEROLE AHEAD OF TIME

This zucchini casserole can be prepared in stages – slice the zucchini, salt the zucchini or you can assemble the entire dish ahead of time:

Slice zucchini. Slice the zucchini into uniform slices and store in an airtight container in the refrigerator for up to 24 hours.
Salt zucchini. Salt the zucchini slices per recipe directions. Line a baking sheet with paper towels followed by a single row of dried zucchini slices. Top with parchment paper and repeat paper towels and zucchini. Cover tightly with plastic wrap and refrigerate. Blot zucchini of any excess moisture before assembling the casserole.
Assemble and Refrigerate. You can assemble the entire zucchini casserole a day ahead of time and refrigerate (without baking). Let the casserole sit on the counter for 30 minutes then bake according to recipe directions, adding an additional 10 minutes.

HOW TO STORE Zucchini Casserole

Let zucchini casserole cool to room temperature and cover tightly with foil. Refrigerate for up to 4 days.

HOW TO REHEAT LEFTOVER Zucchini Casserole

Casserole dish:

Let casserole sit on the counter for 30 minutes while you preheat the oven to 350 degrees F (glass or ceramic dishes can crack if transferred straight from the refrigerator to the oven). This will also help the casserole reheat more evenly.
Cover and bake for 20 minutes or until hot and bubbly.

Single servings:

Transfer a serving of zucchini casserole to a microwave safe plate.
Microwave for 60 seconds then at 20 intervals until warm through.

CAN I FREEZE ZUCCHINI CASSEROLE?

Zucchini casserole should not be frozen before or after baking because zucchini is over 90% water. This means the zucchini will lose structure when thawed and become mushy and a very unappetizing texture.

up close of zucchini casserole scooped in a spoon with bread crumbs

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Tools Used in This Recipe

Cast Iron Braiser 3.5 qt.

Sauce Pan 2.25 qt.

Kitchen Knife Set

Garlic Press

Cheese Grater

See Favorite Tools

Zucchini Casserole

This Zucchini Casserole recipe is the ultimate zucchini side dish to enjoy the bounty of summer zucchini – even your kids will be begging you for seconds! Sliced zucchini is layered in a baking dish, drenched with cheesy cream sauce that has been simmered with herbs and then topped with bubbly golden Gruyere cheese and buttery, crispy panko. This zucchini casserole recipe tastes AMAZING enough for company and special occasions but is simple and easy enough to prepare any night of the week. It also happens to be low carb and can be made gluten free and keto if you skip the panko topping. Best of all, this zucchini casserole is not watery! I’m sharing my fool-proof techniques to prevent watery zucchini casserole so you get nothing but a decadent cocoon of cream sauce – and not a watery bath. This zucchini casserole is also make-ahead friendly and easy to customize the different cheeses, veggies and you can even add protein. In short, your search for the best zucchini casserole recipe stops here!

Servings: servings

Total Time: 1 5

Prep Time: 30

Cook Time: 35

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Ingredients

Zucchini

3 pounds zucchini cut into 1/4-inch slices
1/2 tablespoon kosher salt NOT table salt

Herb Cream

1 cup heavy cream
1/2 tablespoon cornstarch
1 tablespoon chopped fresh chives or 1 tsp. dried
2 tsp garlic cloves, minced or ½ tsp garlic powder
1 tsp EACH dried parsley, onion powder
1/2 tsp EACH dried thyme, dried oregano, salt, pepper
1/4 teaspoon ground nutmeg

ADD LATER

2 oz. (heaping ½ cup) freshly shredded Gruyere cheese
1/2 cup sour cream

Topping

1 oz. (¼ cup) freshly shredded Gruyere cheese
2/3 cup freshly shredded mozzarella cheese
1/2 cup panko breadcrumbs
1 tablespoon melted butter
1 tablespoon olive oil

Instructions

Line sliced zucchini in an even layer on paper towels. Sprinkle evenly with kosher salt; let rest 15 minutes.
Meanwhile, preheat oven to 400 degrees F and grease a 3.5-quart baking dish.
Add all of the “Herb Cream” ingredients EXCEPT sour cream and cheese to a medium saucepan. Bring to a gentle simmer for 3 minutes, stirring often; it will be very thick. Reduce heat to low and add ½ cup Gruyere, stir until melted. Remove from heat and whisk in sour cream until smooth; set aside.
Wipe the salt off of the zucchini slices with a paper towel and dab off the water, pressing firmly.
Arrange half of the zucchini slices in the prepared baking dish. Evenly top with half of the herb cream (it will be thick but will thin once baked). Top with remaining zucchini and remaining cream. Wiggle the dish so that the cream soaks in between the slices.
Top evenly with ¼ cup Gruyere and shredded mozzarella. Cover the baking dish with foil and bake at 400 degrees for 30 minutes.
Meanwhile, melt 1 tablespoon butter in 1 tablespoon olive oil over medium heat in a skillet. Add panko and stir to coat. Continue cooking until crumbs turn golden brown. Transfer to a plate; set aside.
After 30 minutes, remove baking dish from the oven. Remove the foil, top with panko and bake uncovered for an additional 5 minutes or until cheese is melted and bubbling and the zucchini is tender crisp. Remove from oven and let stand 5 minutes before serving. Season with salt and pepper as needed (taste first!).

Notes

TIPS AND TRICKS

Use small to medium zucchini for the best flavor, texture and less water output.
Don’t slice zucchini less than 1/4-inch thick or they will become mushy by the time the cheese is melted and the sauce is bubbly. You can always add more baking time but you can’t undo mushy zucchini!
The zucchini MUST be salted and let to rest for 15 minutes to draw out excess water or your zucchini casserole will be watery.
Use kosher salt to salt the zucchini so it’s easier to wipe off and doesn’t penetrate the zucchini, otherwise your casserole will be salty.
The cream sauce will be thick which is a good thing! The sauce will absorb water released from the zucchini when baked to become the perfect consistency.
Test the zucchini for doneness in the CENTER to make sure they are tender-crisp.
Don’t overbake the zucchini casserole or it will become mushy. Cooking times will vary depending on multiple factors such has the shape/depth of your baking dish, actual zucchini thickness and the zucchini itself.
Do not freeze: Zucchini casserole should not be frozen before or after baking because zucchini is over 90% water. This means the zucchini will lose structure when thawed and become mushy and a very unappetizing texture.

HOW TO PREP AHEAD