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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!
Course Side Dish
Cuisine American
Prep Time 30 minutes
Cook Time 35 minutes
Total Time 1 hour 5 minutes
Servings 8 servings



  • 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 1/2 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


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


  • 1 oz. (1/4 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


  • 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 1/4 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!).



  • 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.


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.


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

How to reheat 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.

How to reheat Single servings: 

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