Zucchini & Yellow Squash Gratin Recipe

Zucchini & Yellow Squash Gratin is a rich, comforting dish that unites the freshest zucchini and yellow squash with a decadently creamy garlic Parmesan sauce, crowned with bubbling mozzarella. Every bite is silky smooth, with tender veggies beneath a cheesy, golden crust that begs for a second helping. Whether served as a luxurious side or a meatless main, it’s the kind of feel-good recipe you’ll want to make all summer long — and possibly all year round!

Ingredients You’ll Need

There’s magic in simplicity, and these ingredients prove it. Each one has a role: infusing flavor, creating creamy texture, or giving that irresistible cheesy finish that crowns any good gratin.

• Zucchini: Always choose firm, glossy zucchini for the freshest flavor and perfect bite in your Zucchini & Yellow Squash Gratin.
• Yellow squash: Brings beautiful color contrast and a subtly sweet note that blends perfectly with the zucchini.
• Olive oil: Just a touch is all you need to soften veggies and coax out their natural flavor.
• Garlic: Freshly minced garlic transforms the cream into a deeply aromatic sauce.
• Yellow onion: Finely chop so it melts into the sauce and lends subtle sweetness in every mouthful.
• Salt: Essential for drawing out the squash’s moisture and enhancing the other flavors.
• Black pepper: Delivers a gentle, warming kick that balances the creamy sauce.
• Heavy cream: The key to luscious richness — it binds everything together in this gratin.
• Grated Parmesan cheese: Adds nutty, salty depth and makes the top extra golden when baked.
• Shredded mozzarella cheese: Melted mozzarella forms that crave-worthy, gooey finish.
• Dried thyme: A sprinkle of thyme brings gentle earthiness, the perfect herbal backdrop for squash.
• Ground nutmeg: Just a pinch! It adds warmth and complexity, enhancing the creamy sauce delightfully.

How to Make Zucchini & Yellow Squash Gratin

Step 1: Prepare Your Baking Dish

Start by preheating your oven to 375°F (190°C). Lightly grease a round or rectangular white baking dish — this small step guarantees your gratin slips right out and maximizes those delicious, golden-brown edges. The right dish makes for easier serving and a picture-perfect presentation.

Step 2: Sauté Onion and Garlic

Pour olive oil into a skillet and set it over medium heat. Once shimmering, add in the finely chopped yellow onion and minced garlic. Sauté for 2–3 minutes, stirring often, until they’re tender and fragrant but not browned. Their aroma is the first taste of the magic to come in your Zucchini & Yellow Squash Gratin.

Step 3: Cook the Squash

Add the thinly sliced zucchini and yellow squash to the skillet. Season with salt, black pepper, and thyme. Stir gently and cook for 5–6 minutes, just until the slices begin to soften but still hold their shape. The seasoning brings every slice to life and ensures each bite is subtly herby and flavorful.

Step 4: Make the Cream Sauce

With the veggies softened, stir in the heavy cream and bring everything to a gentle simmer. Add the nutmeg and half of the Parmesan cheese, stirring to blend while the sauce starts to thicken. The nutmeg will quietly elevate the sauce, hinting at something special without overpowering the fresh squash flavor.

Step 5: Assemble and Bake

Pour the creamy squash mixture into your prepped baking dish, spreading it out evenly. Sprinkle the remaining Parmesan over the top, then shower on the shredded mozzarella cheese. Bake uncovered for 20–25 minutes, until the top is bubbling and gloriously golden brown.

Step 6: Rest and Serve

Remove your Zucchini & Yellow Squash Gratin from the oven and let it rest for a few minutes before serving. This short wait allows the flavors to settle and the creamy layers to slice beautifully — plus, it keeps hungry fingers from burning!

How to Serve Zucchini & Yellow Squash Gratin

Garnishes

A sprinkle of extra Parmesan, a dusting of fresh cracked pepper, or even a handful of chopped fresh herbs like parsley or basil can make your gratin look as good as it tastes. Those little pops of green and sparkle of cheese add freshness and visual flair.

Side Dishes

Although Zucchini & Yellow Squash Gratin shines on its own, it pairs beautifully with grilled chicken, roast salmon, or a crisp green salad. For a vegetarian spread, serve alongside herby quinoa or a simple tomato salad to achieve that perfect balance of hearty and light.

Creative Ways to Present

If you’re hosting friends or want a memorable touch, bake the gratin in individual ramekins for personal servings. For a rustic, family-style presentation, use a sturdy cast iron skillet straight from oven to table. Either way, the sight of that bubbling cheese is always a showstopper.

Make Ahead and Storage

Storing Leftovers

Once cooled, any leftover Zucchini & Yellow Squash Gratin can be transferred to an airtight container and kept in the refrigerator for up to three days. The flavors deepen as they mingle, making it a delightfully easy treat for weeknight reheating.

Freezing

For longer storage, portion the cooled gratin into freezer-safe containers or wrap the baking dish tightly with foil and freeze for up to two months. Thaw overnight in the fridge before reheating. Just keep in mind, the texture may become slightly softer, but the flavor remains spectacular.

Reheating

To bring back that fresh-from-the-oven taste and texture, reheat the gratin uncovered in a 350°F (175°C) oven until warmed through and the cheese is bubbly again. For smaller servings, a quick microwave zap works, but the oven will restore that irresistible top layer.

FAQs

Can I use other types of cheese in Zucchini & Yellow Squash Gratin?

Absolutely! While mozzarella and Parmesan are classics for their melt and flavor, feel free to try Gruyère, cheddar, or even fontina for a different twist. Just keep the total quantity roughly the same.

How thin should I slice the zucchini and squash?

Aim for slices about 1/8 inch thick for the best balance of texture and even cooking. A mandoline slicer can help create perfect, uniform rounds, but a sharp knife works just fine too.

Can I assemble Zucchini & Yellow Squash Gratin ahead of time?

Yes! Prepare everything up to the baking stage, cover and refrigerate for up to a day. When ready, simply bake as directed, adding an extra 5–10 minutes to ensure it’s bubbly and golden.

What can I do if my gratin comes out watery?

Watery gratins are usually from squash releasing too much liquid. Try salting the sliced zucchini and squash and patting them dry before cooking, or simply extend the bake time so excess moisture can evaporate.

Is Zucchini & Yellow Squash Gratin gluten free?

Yes, this recipe contains no flour or breadcrumbs as written, making it naturally gluten free. For added crunch, gluten-free breadcrumbs can be sprinkled on top, if desired.

Final Thoughts

If you’re craving comfort and a little wow-factor from your veggies, Zucchini & Yellow Squash Gratin delivers every single time. It’s easy enough for a weeknight, impressive enough for a special dinner, and always sure to please. Try it out, and don’t be surprised if you find yourself making it again and again!

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