Name: Zucchini and Yellow Squash Au Gratin
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: American
Ingredients: Zucchini; Yellow squash; Garlic; Shallot; Olive oil; All-purpose flour (or gluten-free blend); Whole milk; Freshly grated Parmesan cheese; Sharp white cheddar cheese; Salt; Black pepper; Fresh thyme (optional, for garnish)

This Zucchini and Yellow Squash Au Gratin is a delicious, creamy, and cheesy side dish that turns simple summer squash into something truly special. With a crispy golden top and tender slices of zucchini and yellow squash beneath, it’s a lighter twist on the traditional potato gratin but still packed with flavor.

Why I Love This Recipe

I love how this dish highlights the natural sweetness and tenderness of summer squash while delivering that satisfying richness I usually get from a gratin. It's a great way to use up extra zucchini and yellow squash during the peak season. Plus, it pairs beautifully with grilled meats, roasts, or as a standalone vegetarian option.

ingredients

(Here's a tip: Check out the full list of ingredients and measurements in the recipe card below.)

Zucchini
Yellow squash
Garlic
Shallot
Whole milk
All-purpose flour
Freshly grated Parmesan cheese
Sharp white cheddar cheese
Olive oil
Salt
Black pepper
Fresh thyme (optional, for garnish)

directions

I start by slicing the zucchini and yellow squash thinly and evenly for uniform cooking.
Then I sauté garlic and shallot in olive oil until fragrant.
I sprinkle in the flour to create a roux, then slowly whisk in the milk to form a creamy base.
I remove the pan from heat and stir in a portion of the cheeses until melted.
In a greased baking dish, I layer the zucchini and squash, then pour the cheese sauce evenly over the top.
I finish it off with the remaining cheeses sprinkled over the surface.
The dish goes into a preheated oven at 400°F (200°C) for about 25–30 minutes, until bubbly and golden brown.
For an extra golden crust, I broil it briefly at the end.

Servings and timing

This recipe makes about 6 servings. The prep takes roughly 15 minutes, and the cooking time is around 30 minutes, with an optional 2–3 minutes under the broiler.

Variations

I sometimes add breadcrumbs on top before baking for an extra crunch. Mixing in other cheeses like Gruyère or mozzarella gives it a different flavor profile. For a heartier version, I’ve also layered in some cooked quinoa or even thin slices of cooked potato.

storage/reheating

I store leftovers in an airtight container in the refrigerator for up to 3 days. To reheat, I use the oven at 350°F (175°C) until warmed through, or I microwave it in short intervals, though the oven keeps the top nice and crispy.

FAQs

How do I keep the squash from getting watery?

I usually salt the slices and let them sit for 10 minutes, then pat them dry to reduce moisture.

Can I use just zucchini or just yellow squash?

Yes, I’ve used only zucchini or only yellow squash when that’s what I had on hand. It works just as well.

Can I make this recipe ahead of time?

I often prepare it up to the baking step, cover it, and refrigerate it. Then I bake it just before serving.

What’s the best cheese to use?

I like sharp cheddar for bold flavor and Parmesan for a salty kick. Gruyère also works beautifully if I want something fancier.

Can I make this dish gluten-free?

Yes, I use a gluten-free flour blend in the roux or substitute with cornstarch for thickening.

Conclusion

Zucchini and Yellow Squash Au Gratin is one of my go-to comfort dishes that still feels light and fresh. It's creamy, cheesy, and full of garden flavor. Whether I’m making it for a weeknight dinner or a special gathering, it’s always a hit.