Cheesy Zucchini Gratin Recipe

Cheesy zucchini gratin baked in casserole dish with a golden bubbly crust.

This easy, cheesy zucchini gratin recipe is the ultimate comfort food side dish. Sliced fresh zucchini is baked in a velvety, homemade cream sauce and finished with a golden, bubbling crust of melted Gruyère and Parmesan cheese. Perfect for weeknight dinners or a cozy holiday side, it’s a delicious way to enjoy fresh vegetables, Mediterranean-style!

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Prep Time 15

Cook Time 35

Servings: 6

Course: Side Dish

Cuisine: Greek

Calories: 340

Ingredients Method Notes

Ingredients

4 medium zucchini sliced into 1/4-inch rounds
1 ½ cups whole milk or heavy cream for extra richness
2 cloves garlic minced
2 tbsp unsalted butter
2 tbsp all-purpose flour
2 cups shredded Gruyère or Swiss cheese divided
½ cup freshly grated Parmesan cheese
1 tsp salt
½ tsp black pepper
¼ tsp ground nutmeg
2 tsp fresh thyme or Italian seasoning

Method

Preheat & Prep: Heat your oven to 375°F (190°C). Grease a medium baking dish (9x9 or similar) with butter.
Make the Sauce: In a saucepan over medium heat, melt the butter and sauté the garlic for 1 minute until fragrant. Whisk in the flour and cook for 1-2 minutes until bubbling. Slowly pour in the milk/cream while whisking constantly to avoid lumps. Simmer for 1 minute until thickened. Remove from heat; stir in 1 cup of Gruyère and all the Parmesan until smooth.
Layer: Arrange a layer of slightly overlapping zucchini slices in the dish. Season with salt and pepper. Pour over one-third of the cheese sauce. Sprinkle with a bit of Gruyère and herbs. Repeat for 2–3 layers until all zucchini and sauce are used.
Bake: Top with the remaining Gruyère and herbs. Bake for 25–30 minutes until the zucchini is tender and the top is golden brown and bubbly.
Serve: Let the dish rest for 5 minutes before serving to allow the sauce to thicken and set.

Notes

Preventing Watery Gratin: For the best texture, salt your zucchini slices lightly, let them sit for 10 minutes, then pat them dry with a paper towel before layering. This removes excess moisture and ensures your creamy cheese sauce doesn't become soupy.
Cheese Substitution: While we recommend Gruyère, Swiss, and Parmesan, you can substitute other high-melt cheeses like Fontina or Provolone.
Make-Ahead Tip: You can assemble the dish up to 24 hours in advance. Cover and refrigerate, then add 5-10 extra minutes to the bake time when cooking.