Yellow Squash and Zucchini Casserole with Creamy Cheddar Cheese Sauce

Yellow Squash and Zucchini Casserole

If you have a basket of summer squash sitting on the counter, this is the casserole I want you to make first. Tender slices of yellow squash and zucchini bake in a velvety cheddar and Parmesan sauce, then finish under a golden breadcrumb crust. Dried thyme and a pinch of red pepper flakes keep every bite from tasting flat.

this …

It is a beginner friendly side dish, the kind you can pull together after work without studying a technique book. Serve it next to roasted chicken, or let it star on its own with a crisp green salad. Grab your baking dish and let’s get cooking.

Key Ingredients

You need fourteen items here, and most of them are probably already in your kitchen. The stars are 1 lb yellow squash and 1 lb zucchini. Together they give you about two pounds of tender vegetable that softens into the sauce without turning to mush.

Aromatics come next: 1 medium onion and 2 cloves garlic. The onion sweetens as it cooks and the garlic keeps everything savory and warm.

The sauce is a simple stir together mix of 1 cup milk, 8 ounces shredded cheddar cheese, 4 ounces grated Parmesan cheese, and 2 tablespoons butter. You use half of the Parmesan inside the sauce and save the rest for the topping, which is where the magic lies in its simplicity.

For the crust you need 1 cup breadcrumbs. They go on dry, straight from the bag, so the top crisps up as the casserole bakes.

Seasoning rounds it out: 1 teaspoon salt, 1/2 teaspoon black pepper, 1/2 teaspoon dried thyme, and 1/4 teaspoon red pepper flakes. You also need 1 tablespoon olive oil for the skillet.

How To Make Yellow Squash and Zucchini Casserole

This comes together in about 15 minutes of prep, then the oven does the rest. You will need a large skillet, a mixing bowl, and a greased 9×13 inch baking dish. The whole thing bakes in 25 to 30 minutes, and your kitchen will smell amazing while it works.

1. Preheat the oven to 375°F.
2. Slice the yellow squash and zucchini into 1/4 inch rounds.
3. Heat the 1 tablespoon olive oil in a large skillet over medium heat and add the squash and zucchini.
4. Season with salt and black pepper and cook for about 5 minutes, stirring occasionally, until the edges soften.
5. Add the chopped onion and minced garlic to the skillet and cook until the onion is translucent.
6. Stir in the dried thyme and red pepper flakes, then remove the skillet from the heat.
7. In a mixing bowl, combine the milk, shredded cheddar cheese, half of the Parmesan cheese, and the melted butter until smooth.
8. Transfer the cooked vegetables to a greased 9×13 inch baking dish and pour the cheese mixture over the top, stirring gently to coat.
9. Sprinkle the breadcrumbs and the remaining Parmesan cheese evenly over the casserole.
10. Bake for 25 to 30 minutes, until the top is golden brown and the casserole is bubbly around the edges.
11. Let the casserole rest for 5 minutes before serving.

Give the vegetables a little room in the skillet rather than piling them up. Crowding traps steam, and steam is what makes a squash casserole watery. If your pan is on the small side, cook the squash in two batches.

The cheese mixture will look loose when you pour it. That is exactly what you want, because it thickens as it bakes and coats every slice. When you stir it in, use a gentle hand so the rounds stay mostly whole.

Serving Suggestions

This casserole is a natural fit for a family feast. Set it beside roasted chicken or baked ham and watch it disappear from the table. The creamy sauce plays nicely with the salty edge of a glazed ham.

Heading to a potluck? Carry it right in the baking dish with a serving spoon and a stack of small plates. It holds heat well and tastes just as good at room temperature.

For a vegetarian spread, pair it with a crisp mixed green salad and warm garlic bread. The cool crunch of the salad balances the rich cheese sauce beautifully.

Brunch works too. Cut it into warm squares and add a dollop of herbed sour cream with fresh chopped chives on top. It turns a simple side into something guests will ask about.

Tips For Perfect Yellow Squash and Zucchini Casserole

Start with fresh summer squash and zucchini. Firm, glossy vegetables hold their shape better and taste sweeter than anything that has been sitting in the fridge for two weeks.

Want a milder, creamier result? Swap Monterey Jack or mozzarella for the cheddar. Asiago or Pecorino Romano work in place of the Parmesan if you like a sharper finish.

For a gluten free version, use certified gluten free breadcrumbs or crushed gluten free crackers. Panko gives you extra crunch if you are not avoiding gluten.

Optional moisture tip: after slicing, sprinkle the squash lightly with salt, let it sit in a colander for 10 minutes, then press it dry with paper towels.

Leftovers keep in an airtight container in the refrigerator for up to three days.

How To Store It

Let the casserole cool first, then refrigerate it in an airtight container for up to three days. Cold casserole reheats surprisingly well because the sauce stays soft.

To freeze, cool it completely, then wrap the dish tightly in plastic wrap followed by foil. It keeps for up to two months. Move it from the freezer to the refrigerator overnight to thaw.

Reheat uncovered at 375°F for 20 to 25 minutes until heated through, or microwave individual portions for 1 to 2 minutes. For a gentler reheat, place leftovers on an oven safe dish at 350°F for 10 to 12 minutes.

You can also assemble the whole casserole ahead of time, cover it, and refrigerate it for up to 24 hours. Add about 5 extra minutes to the bake time when it goes in cold.

What Makes This Special

It comes down to a handful of good things working together: fresh squash, two cheeses, a hint of spice, and a crunchy breadcrumb top that gives you a little texture in every forkful. Nothing here is fussy, and that is the point.

I like to add protein on busy nights by stirring cooked shredded chicken, crumbled cooked sausage, or cooked bacon pieces in with the vegetables and cheese mixture. Reduce the milk slightly so the sauce stays thick and creamy.

If you want to see where this recipe started, the original version lives at TasteByJulia.

Save this one, and tell me how it turned out in the comments. I love hearing which swaps you tried and what you served alongside it.

FAQs

Yellow Squash and Zucchini Casserole

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

No reviews

Print Recipe

Pin Recipe

Yellow Squash and Zucchini Casserole If you have a basket of summer squash sitting on the counter, this is the casserole I want you to make first. Tender slices of yellow squash and zucchini bake in a velvety cheddar and Parmesan sauce, then finish under a golden breadcrumb crust.

• Total Time: 50 min
• Yield: 8 1x

Ingredients

Scale 1x2x3x

1 lb yellow squash
1 lb zucchini
1 medium onion
2 cloves garlic
8 ounces shredded cheddar cheese
4 ounces grated Parmesan cheese
1 cup breadcrumbs
1 cup milk
2 tablespoons butter
1 tablespoon olive oil
1 teaspoon salt
1/2 teaspoon black pepper
1/2 teaspoon dried thyme
1/4 teaspoon red pepper flakes

Cook Mode Prevent your screen from going dark

Instructions

1-Preheat the oven to 375°F: Preheat the oven to 375°F.
2-Slice the yellow squash and zucchini into: Slice the yellow squash and zucchini into 1/4-inch rounds.
3-Heat the olive oil in a large: Heat the olive oil in a large skillet over medium heat and add the squash and zucchini.
4-Season with salt and black pepper and: Season with salt and black pepper and cook for about 5 minutes, stirring occasionally.
5-Add the chopped onion and minced garlic: Add the chopped onion and minced garlic to the skillet and cook until the onion is translucent.
6-Stir in the dried thyme and red: Stir in the dried thyme and red pepper flakes and remove the skillet from heat.
7-In a mixing bowl, combine the milk,: In a mixing bowl, combine the milk, shredded cheddar cheese, half of the Parmesan cheese, and melted butter.
8-Transfer the cooked vegetables to a greased: Transfer the cooked vegetables to a greased 9×13-inch baking dish and pour the cheese mixture over the top, stirring gently to coat.
9-Sprinkle the breadcrumbs and remaining Parmesan cheese: Sprinkle the breadcrumbs and remaining Parmesan cheese evenly over the casserole.
10-Bake for 25 to 30 minutes until: Bake for 25 to 30 minutes until the top is golden brown and the casserole is bubbly.
11-Let the casserole rest for 5 minutes: Let the casserole rest for 5 minutes before serving.

Last Step:

Please leave a rating and comment letting us know how you liked this recipe! This helps our business to thrive and continue providing free, high-quality recipes for you.

• Prep Time: 15 min
• Cook Time: 35 min
• Method: bake