Dinner

Easy Cheesy Zucchini Gratin Recipe

Byluca Carter April 3, 2026April 3, 2026

Introduction

Cheesy Zucchini Gratin is a comforting, creamy baked side dish that elevates fresh zucchini into a rich and flavorful casserole. With layers of tender zucchini, a savory cheese sauce, and a crisp golden topping, this recipe is perfect for cozy family dinners or special occasions. It’s a delicious way to make vegetables feel special and satisfying.

A round white pan filled with layered zucchini slices topped with melted, bubbly golden-brown cheese. The layers include green zucchini rounds covering the base, a creamy white cheese sauce in between, and a thick top layer of browned cheese with small green herb flakes sprinkled throughout. A wooden spatula lifts a stack of three cheesy zucchini slices, showing stretchy melted cheese strings between the pan and the spatula. The background has a white marbled texture. photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 pounds zucchini, sliced into 1/4-inch rounds
1 teaspoon salt, divided

2 tablespoons unsalted butter
1 small yellow onion, finely diced

3 cloves garlic, minced
1 tablespoon all-purpose flour

1 cup heavy cream
1/2 cup whole milk
1/2 teaspoon black pepper

1/4 teaspoon ground nutmeg
1 teaspoon dried thyme or 1 tablespoon fresh thyme leaves
1 cup shredded mozzarella cheese

1/2 cup shredded sharp cheddar cheese
1/2 cup grated Parmesan cheese, divided
1/2 cup panko breadcrumbs

1 tablespoon olive oil
2 tablespoons chopped fresh parsley, for garnish

Instructions

Step 1: Preheat your oven to 375°F (190°C) and lightly grease a 9 x 13-inch baking dish. Place the sliced zucchini in a large bowl, sprinkle with 1/2 teaspoon salt, and toss to coat. Spread the zucchini over paper towels or clean kitchen towels and let it rest for 20 to 30 minutes to draw out excess moisture. Pat dry thoroughly before using.

Step 2: In a large skillet over medium heat, melt the butter. Add the diced onion and sauté for 4 to 5 minutes until softened. Stir in the minced garlic and cook for 30 seconds until fragrant.
Step 3: Sprinkle the flour over the onion and garlic mixture and cook, stirring constantly, for about 1 minute to eliminate the raw flour taste.
Step 4: Slowly pour in the heavy cream and milk, whisking constantly until smooth. Add the remaining 1/2 teaspoon salt, black pepper, ground nutmeg, and thyme. Let the sauce simmer gently for 2 to 3 minutes until it thickens slightly.

Step 5: Remove the skillet from heat and stir in the mozzarella, cheddar, and 1/4 cup of the Parmesan cheese until melted and the sauce is creamy.
Step 6: Arrange half of the zucchini slices evenly in the prepared baking dish. Spoon half of the cheese sauce over the zucchini. Add the remaining zucchini in a single layer, then spread the remaining sauce on top.
Step 7: In a small bowl, combine the panko breadcrumbs, olive oil, and the remaining 1/4 cup Parmesan cheese. Sprinkle this mixture evenly over the gratin.

Step 8: Bake uncovered for 30 to 35 minutes, or until the gratin is bubbly around the edges and the topping is golden brown. For extra color, broil for 1 to 2 minutes at the end, watching closely to avoid burning.
Step 9: Let the gratin rest for 10 minutes before serving. Just before serving, sprinkle with chopped fresh parsley for a bright finish.

Tips & Variations

Salting and patting dry the zucchini is key to preventing a watery gratin and ensuring a creamy texture.

Use freshly shredded cheese instead of pre-shredded for better melting and flavor.
Swap the cheddar for Gruyère for a nuttier flavor or Monterey Jack for a milder finish.
Add thinly sliced yellow squash or a handful of baby spinach between layers for variation.

For extra herb flavor, stir in chopped basil, chives, or rosemary into the sauce.
Replace olive oil with melted butter in the breadcrumb topping for a richer crisp crust.

Storage

Allow any leftover gratin to cool completely, then cover and refrigerate for up to 3 days. Reheat in a 350°F (175°C) oven for 15 to 20 minutes until warmed through, which helps keep the topping crisp. You can also microwave portions for convenience, though the topping may soften. For make-ahead cooking, assemble without the breadcrumb topping and refrigerate up to 24 hours; add topping before baking to maintain crispness.

How to Serve

A dish in a round white baking dish filled with layers of green zucchini slices topped with a thick layer of melted, golden-brown cheese that is bubbly and slightly browned in spots. One layer shows zucchini slices covered in creamy white cheese with some green herbs sprinkled on top. A woman's hand is lifting a portion with a wooden spatula, and stringy, melted cheese stretches from the dish to the lifted portion. The background is a white marbled texture. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I make cheesy zucchini gratin ahead of time?

Yes, this gratin can be assembled several hours or a day in advance. For best results, prepare and layer all ingredients except the breadcrumb topping. Add the topping just before baking so it remains crisp. If refrigerated assembled, allow it to sit at room temperature for 20-25 minutes before baking and add extra baking time if needed.

Why is my zucchini gratin watery?

Watery gratin usually results from excess moisture in the zucchini or under-thickened sauce. Salting the sliced zucchini and letting it rest before drying thoroughly helps remove water. Also, ensure the cream sauce simmers until slightly thickened before assembling. Avoid overcrowding the dish and let the baked gratin rest to firm up before serving.