Healthy Yellow Summer Squash Casserole Recipe with Cheesy Breadcrumb Topping

Name: Healthy Yellow Summer Squash Casserole
Prep time: 15 min
Cook time: 1 h 5 min
Total time: 1 h 20 min
Yield: 6
Ingredients: 1 clove garlic, peeled; 2 slices sourdough bread, about 3 to 4 ounces; 2 tablespoons extra-virgin olive oil; 6 medium summer squash, about 3 pounds, cut into rounds; 1 small ripe tomato, diced; 2 tablespoons chopped fresh basil, plus more for garnish; 1 1/2 teaspoons coarse kosher salt, or to taste; Freshly ground pepper, to taste; 4 ounces shredded Italian blend cheese, 1 cup; 1/2 cup shredded Parmesan cheese

By:

Ruby Bennett

Published:

September 7, 2026

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Healthy Yellow Summer Squash Casserole

This recipe is my favorite answer when the garden gives me more yellow squash than I know what to do with. A healthy yellow summer squash casserole made with tender sliced rounds, melted cheese, fresh basil, and a golden breadcrumb topping.

It works as a side dish for picnics, potlucks, or summer dinners when you want something warm and comforting without spending hours in the kitchen.

You can even assemble it ahead of time and tuck it in the fridge to bake later, which makes it perfect for busy weeknights or weekend gatherings.

The breadcrumb topping gives it a pleasing crunch, while the squash softens into delicate bites that soak up all the basil and garlic flavor.

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Why We Love This Recipe for Healthy Summer Squash Casserole

I created this recipe when my garden overflowed with bright yellow squash a few summers ago. I already had a reliable zucchini casserole that my family enjoyed, so I decided to adapt it by swapping in summer squash and adding sourdough breadcrumbs, fresh basil, and a mix of Italian cheeses.

The result turned out even better than I hoped, and now it is a regular at our table from late June through early September.

This casserole feels special enough for company but is simple enough for a Tuesday night. I love serving it alongside grilled Cajun Flank Steak when we have friends over, or with Barbecue Chicken at family cookouts.

On lighter evenings, it pairs beautifully with Garlic Lemon Chicken and a crisp green salad. The squash keeps its delicate texture while the breadcrumb topping adds a savory crunch that contrasts nicely with the tender vegetables underneath.

What I appreciate most is how the breadcrumbs absorb the natural moisture from the squash, eliminating any need for eggs or fillers while keeping the casserole cohesive and easy to slice.

My kids even ask for seconds, which is the highest praise a vegetable dish can get in our house.

Key Ingredients for this Recipe

Yellow Summer Squash

The star of the show is six medium yellow summer squash, which comes to about three pounds once you cut them into rounds.

Garden squash varies in size, so I always weigh mine on the kitchen scale to be sure I have enough for a full 9 by 13 inch dish.

These sunny rounds form the flavorful, nutritious base of the casserole and become fork tender as they bake under a blanket of cheese and breadcrumbs.

Sourdough Bread

Instead of the traditional Ritz cracker and butter topping, this version relies on a healthier breadcrumb made from two slices of sourdough bread. I tear the slices into pieces and pulse them in the food processor until they turn into coarse crumbs.

The dry sourdough soaks up moisture from the squash as it bakes and helps bind the filling together. This means no eggs or additional fillers are needed to hold the casserole, and you still get that golden, crunchy topping everyone loves.

The mild tang of sourdough works beautifully with the sweet squash and savory cheese.

Cheese

Because summer squash releases quite a bit of water as it cooks, I do not add any cream sauce or heavy cream. Richness comes from cheese alone, keeping the dish lighter while still tasting indulgent.

I use a combination of shredded Italian blend cheese, look for packages labelled Italian Blend or Pizza Blend at the grocery store, plus freshly shredded Parmesan. Together they deliver plenty of flavor without introducing extra moisture, so the casserole stays cohesive rather than turning soupy.

The Parmesan in particular gives the golden topping that irresistible savory depth.

Step By Step Instructions For Making This Squash Casserole

I have made this casserole enough times that the steps now feel like second nature, but the first time I tried it I was pleasantly surprised by how straightforward the process is.

The food processor does most of the work for the topping, and layering the ingredients takes only a few minutes. Here is exactly how I put it together from start to finish.

Step 1: Blend Breadcrumbs

Preheat your oven to 375 degrees F so it is ready when you are. Fit your food processor with the steel blade attachment, then drop a peeled garlic clove through the feed tube while the motor runs to mince it finely.

Remove the lid, tear two slices of sourdough bread into three or four pieces each, and add them to the bowl. Process until the bread turns into coarse crumbs. With the motor still running, drizzle in two tablespoons of extra virgin olive oil.

This mixture works double duty, it absorbs liquid from the squash during baking and later becomes the crunchy golden topping we are after.

Set aside about half of this breadcrumb mixture, roughly ¾ cup, keeping the rest for the final topping.

Step 2: Combine Ingredients

In a large bowl, toss the reserved ¾ cup of breadcrumb mixture with the sliced yellow squash rounds, one small diced ripe tomato, two tablespoons of chopped fresh basil, one and a half teaspoons of coarse kosher salt, and freshly ground pepper to taste.

Use your hands or a large spoon to mix everything gently until the squash rounds are evenly coated. The tomato and basil add little bursts of freshness that brighten the whole dish.

Step 3: Assemble Casserole and Bake

Coat a 9 by 13 inch casserole dish, or one of similar volume, with cooking spray. Spread half of the squash mixture evenly across the bottom, then sprinkle half of the shredded Italian blend cheese over the top.

Add the remaining squash mixture and press it down gently. Do not add the final cheese layer just yet. Cover the dish tightly with foil and slide it into the preheated oven.

Bake until the squash is fork tender, about 50 to 55 minutes. The foil traps steam and helps the squash cook through without drying out.

Step 4: Add Topping and Bake Until Done

When the squash is tender after about 50 minutes, increase the oven temperature to 450 degrees F. Carefully remove the foil, then scatter the remaining shredded Italian blend cheese, the half cup of shredded Parmesan, and the reserved breadcrumb mixture over the top.

Return the dish to the oven uncovered and bake until the cheese melts into a golden layer and the breadcrumbs turn crisp and brown, about 12 to 15 minutes more.

Healthy Yellow Summer Squash Casserole, Step 4: Add Topping and Bake Until Done

Let it rest for a few minutes before scooping, so the slices hold together on the plate.

Variations To Try

I like to change this casserole depending on what is in season or what I am craving. Here are a few ways you can adapt it.

Bell pepper: Dice one bell pepper and sauté it in a small skillet until tender, then let it cool slightly and stir it into the squash mixture along with the tomato. It adds a mild sweetness and extra color.
Richer flavor: Swap the olive oil for melted butter when making the breadcrumb mixture. It gives the topping a more decadent, buttery taste that reminds me of holiday stuffing.
Sharp cheddar: Replace the Italian blend cheese with shredded extra sharp cheddar. The tangier cheese pairs especially well with the sweet squash and basil.
Mixed squash: Use half zucchini and half yellow squash for a multicolored effect, or mix in patty pans and yellow zucchini when your garden gives you an assortment.
Sweet corn: Cut the kernels from two ears of fresh sweet corn and toss them with the squash and breadcrumb mixture. The corn adds a pop of juicy sweetness that tastes like peak summer.
Vidalia onion: Thinly slice a Vidalia onion and sauté it in one tablespoon of butter over medium low heat until softened, about eight minutes, then spread it on top of the casserole before covering with foil and baking. The onions turn silky and sweet as they cook.

Additional Recipes to Try

If you enjoy this casserole, I have plenty of other squash recipes to carry you through the season and beyond. For a lighter grilled option, try Low Carb Grilled Summer Squash Boats with a sprinkle of herbs.

My Chicken Tortilla Skillet works summer squash into a one pan dinner that my family requests often. When cooler weather arrives, I turn to Butternut Squash Macaroni and Cheese for pure comfort, or a Butternut Squash Lasagna that you can assemble up to two days ahead.

Healthy Yellow Summer Squash Casserole, Additional Recipes to Try

For a quick side dish, Cheesy Stovetop Butternut Squash comes together in about forty minutes, and simple Roasted Butternut Squash is ready in ten minutes with a vegan, paleo, and gluten free preparation.

On busy nights, Easy Sautéed Zucchini takes just twelve minutes and pairs with nearly anything. Each recipe celebrates squash in a different way, so you will never run out of inspiration.

FAQs

How do you keep yellow squash casserole from getting watery?

The breadcrumb topping absorbs excess moisture as the casserole bakes. This recipe tosses half the homemade sourdough breadcrumbs with the squash before layering, which helps bind the dish without needing eggs or fillers. The initial covered bake at 375°F for 50 to 55 minutes allows the squash to steam and tenderize while the crumbs soak up the released liquid.

Can you make this yellow squash casserole ahead of time?

Yes, you can assemble the casserole up to 8 hours ahead and keep it covered in the refrigerator. Store the reserved breadcrumb mixture separately in an airtight container. When ready to bake, add the reserved crumbs and cheese topping just before placing the dish in the oven, then follow the original baking instructions.

What cheese works best for a healthy summer squash casserole?

A combination of shredded Italian blend cheese and shredded Parmesan cheese provides rich flavor and excellent melt without introducing extra moisture. The Italian blend, typically mozzarella and provolone, gives a gooey texture, while Parmesan adds sharp, salty depth. Shredding cheese from a block rather than using pre-shredded varieties ensures the smoothest melt.

Is crookneck squash the same as yellow squash for this casserole?

Yes, crookneck squash is a type of yellow summer squash and works perfectly in this recipe. Both straightneck and crookneck varieties have thin, edible skins and a mild flavor with high water content. Select firm, blemish-free squash about 6 to 8 inches long for the best texture and fewest seeds.

Healthy Yellow Summer Squash Casserole Recipe with Cheesy Breadcrumb Topping

Healthy Yellow Summer Squash Casserole

Why We Love This Recipe for Healthy Summer Squash Casserole