Zucchini Gratin Recipe

If you’re looking to impress at your next dinner, trust me: this Zucchini Gratin is about to become your go-to crowd-pleaser. Imagine layers of tender zucchini, sweet golden onions, and a luscious creamy sauce—all crowned with a bubbling, crisp blanket of Gruyere and bread crumbs. The flavors are rich, the texture is irresistibly velvety, and that golden crust? Simply unbeatable! Whether you’re trying to use up a zucchini haul or you’re in the mood for a comforting side dish that feels like a little luxury, the Zucchini Gratin absolutely delivers.

Zucchini Gratin Recipe - Recipe Image

Ingredients You’ll Need

One of the best things about Zucchini Gratin is how it turns everyday ingredients into something totally memorable. Each element plays an important role, balancing fresh flavors with indulgent touches and giving you the perfect savory bite every time.

  • Butter: Adds richness and helps develop the onions’ deep, sweet flavor as they slowly cook.
  • Yellow Onions: When caramelized, these become soft and sweet, forming the foundation of the dish’s flavor.
  • Zucchini and/or Yellow Squash: Sliced thin, these make up the heart of the gratin, offering tender layers and subtle freshness.
  • Kosher Salt: Enhances every ingredient; use less if you have only table salt on hand.
  • Freshly Ground Black Pepper: Adds just the right amount of warmth and zing.
  • Ground Nutmeg: A pinch is all you need to give the creamy sauce a hint of complexity.
  • Garlic: Lends a savory depth that infuses the layers with classic comfort.
  • All-Purpose Flour: Thickens the sauce, making it perfectly creamy but not heavy.
  • Warm Milk: Helps the sauce come together quickly, staying smooth and glossy.
  • Italian Style Bread Crumbs: Create that crisp, irresistible topping with a hint of Italian seasoning.
  • Grated Gruyere: Melts into gooey bliss on top, its nutty flavor giving the Zucchini Gratin a truly special finish.

How to Make Zucchini Gratin

Step 1: Preheat and Prep

Before you get started, preheat your oven to 400 degrees F. This ensures the gratin will cook evenly and develop that beautiful golden crust. While the oven warms up, slice your onions and zucchini—the thinner, the better for melting layers!

Step 2: Caramelize the Onions

Melt the butter in a very large sauté pan over low heat. Add the sliced onions and let them cook gently for about 20 minutes. Stir occasionally; you’re aiming for soft, tender onions without any browning. As the onions mellow and sweeten, take the opportunity to prep your other ingredients.

Step 3: Cook the Zucchini

Once the onions are perfectly silky, add the sliced zucchini (and yellow squash, if using). Cover the pan and cook for 8 to 10 minutes until the zucchini is just tender. Don’t worry if it looks like a lot at first; it cooks down beautifully. Uncover, then stir in the salt, pepper, nutmeg, and garlic. Let everything cook together for another five minutes, uncovered, so the zucchini can pick up all those savory flavors.

Step 4: Make the Creamy Sauce

In a separate bowl or measuring cup, whisk the flour into the warm milk until there are no lumps. Pour this mixture into your pan with the zucchini and onions, turning the heat up slightly. Let the sauce heat until it starts to bubble, then reduce the heat back to low and cook for a couple of minutes. You’ll watch it transform into a creamy coating that brings every bite together.

Step 5: Assemble and Bake the Gratin

Transfer your luscious zucchini mixture, along with all the sauce, into an 8 by 10-inch baking dish (or the closest size you have). Now, combine the bread crumbs with the grated Gruyere and sprinkle this mixture generously over the top. For extra flavor and browning, drizzle a bit of olive oil over the surface. Pop your dish into the oven and bake for 20 minutes, or until everything is bubbly and gloriously browned. Allow the Zucchini Gratin to cool for a few minutes before serving so every slice holds together.

How to Serve Zucchini Gratin

Zucchini Gratin Recipe - Recipe Image

Garnishes

Top your Zucchini Gratin with a sprinkle of fresh herbs like parsley, chives, or even a touch of thyme. This not only gives it a burst of color but also adds brightness that cuts through the richness. A little extra Gruyere or freshly cracked black pepper never hurts for those who can’t get enough.

Side Dishes

This gratin is wonderfully versatile—think of it alongside roasted chicken, grilled steak, or a simple salad tossed with a lemony vinaigrette. It’s also perfect next to a hearty soup when you want a meal that’s warm and nourishing.

Creative Ways to Present

For a casual family style, serve the Zucchini Gratin straight from the baking dish at the table, letting everyone dig in. Fancy things up by spooning individual servings into small ramekins or bowls, or try stacking grilled vegetables beside for a summery presentation. Even on a brunch buffet, mini gratins would absolutely steal the show!

Make Ahead and Storage

Storing Leftovers

If you’re lucky enough to have leftovers, let the Zucchini Gratin cool completely before covering and storing it in the refrigerator. It’ll keep well for up to three days, maintaining its creaminess and those dreamy flavors.

Freezing

While Zucchini Gratin can be frozen, keep in mind that the texture may soften upon thawing. If you wish to freeze, wrap it tightly and store for up to a month. For best results, freeze before baking and add the bread crumb topping fresh before it goes in the oven.

Reheating

To reheat, cover the dish loosely with foil and warm it in a 350 degree F oven until heated through. In the last few minutes, uncover to restore that crispy topping. Individual portions can also be gently reheated in the microwave, though the topping will be softer.

FAQs

Can I use only zucchini or just yellow squash?

Absolutely! Use whichever you have on hand, or mix both for added color and flavor. The recipe works equally well with all zucchini or all yellow squash.

What can I use instead of Gruyere?

While Gruyere gives Zucchini Gratin its signature flavor, you can swap it for Swiss, Fontina, or sharp white cheddar in a pinch—it’ll still melt beautifully and taste delicious.

Can I make Zucchini Gratin ahead of time?

Yes! You can assemble the gratin (without baking) and refrigerate it for up to a day in advance. When ready, simply add the bread crumb topping and bake as directed.

Is this recipe gluten free?

To make your Zucchini Gratin gluten free, use your favorite gluten free flour blend in place of the all-purpose flour and gluten free Italian style bread crumbs for the topping.

How do I keep the gratin from being watery?

Slice your zucchini as directed and cook them uncovered for a few minutes, as in the recipe. This step lets excess moisture evaporate so your Zucchini Gratin stays rich and creamy, not watery.

Final Thoughts

Once you’ve tasted homemade Zucchini Gratin, you’ll wonder how you ever settled for ordinary side dishes. It’s comforting, spectacularly flavorful, and just plain fun to make. Give this recipe a try—you’re just a few steps away from a golden, bubbling pan of absolute deliciousness!

Print

Zucchini Gratin Recipe

This creamy and flavorful Zucchini Gratin is a perfect side dish for any meal. Layers of tender zucchini, caramelized onions, and a cheesy breadcrumb topping make this dish a crowd-pleaser.

  • Author: Maya
  • Prep Time: 30 minutes
  • Cook Time: 40 minutes
  • Total Time: 1 hour 10 minutes
  • Yield: 6 servings 1x
  • Category: Side Dish
  • Method: Baking
  • Cuisine: French
  • Diet: Vegetarian

Ingredients

Scale

For the Gratin:

  • 6 tablespoons butter
  • 1 pound yellow onions, cut in half and sliced (about 3 large)
  • 2 pounds zucchini and/or yellow squash, sliced 1/4-inch thick (about 4 medium zucchini)
  • 2 teaspoons kosher salt (use 1/2 teaspoon if using table salt)
  • 1/2 teaspoon freshly ground black pepper
  • 1/4 teaspoon ground nutmeg
  • 2 cloves garlic, finely minced or pressed
  • 2 tablespoons all-purpose flour
  • 1 cup warm milk
  • 3/4 cup Italian-style bread crumbs
  • 3/4 cup grated Gruyere

Instructions

  1. Preheat the oven: Preheat the oven to 400 degrees F.
  2. Caramelize the onions: Melt butter in a large sauté pan, cook onions over low heat for about 20 minutes until tender but not browned.
  3. Cook the zucchini: Add zucchini to the pan, cover, and cook for 8-10 minutes until tender. Add salt, pepper, nutmeg, and garlic, then cook uncovered for 5 more minutes.
  4. Make the sauce: Whisk flour into warm milk, add to the pan, and cook until thickened.
  5. Assemble the gratin: Pour the zucchini mixture into a baking dish. Combine bread crumbs and Gruyere, sprinkle on top, drizzle with olive oil, and bake for 20 minutes until golden brown.
  6. Serve: Allow the gratin to cool slightly before serving.

Notes

  • This dish can be made ahead of time and reheated before serving.
  • Experiment with different types of cheese for varied flavors.

Nutrition

  • Serving Size: 1 serving
  • Calories: 320
  • Sugar: 8g
  • Sodium: 640mg
  • Fat: 20g
  • Saturated Fat: 12g
  • Unsaturated Fat: 6g
  • Trans Fat: 0g
  • Carbohydrates: 25g
  • Fiber: 3g
  • Protein: 12g
  • Cholesterol: 55mg

Keywords: Zucchini Gratin, Side Dish, Vegetarian, French Cuisine, Baked Zucchini

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