Summer Squash Casserole

Summer squash casserole has been on my table more times than I can count. It’s the kind of dish that gets scooped up before anything else—and no one ever leaves a bite behind.

It’s warm, cheesy, and golden on top, with that soft, mellow squash underneath. I’ve made this for family dinners, brought it to neighbor potlucks, and served it right alongside holiday roasts.

Every time, it disappears fast and someone always asks for the recipe before dessert is even on the table.

This version is exactly how I’ve come to love it over the years. The squash gets cooked just enough to soften, but not so much that it turns to mush.

The cheese melts into the mixture, giving it that creamy, rich middle layer. And the buttery cracker topping? It bakes into a crisp, golden crust that makes the whole thing come together perfectly.

If you’ve never tried a casserole like this before, you’ll be surprised how much flavor a dish this simple can hold.

And if you’ve had it many times before—this one just might become your go-to version.

Table of Contents

Summer Squash Casserole Recipe

Ingredients

6 cups yellow summer squash, sliced into thin half-moons (about 4–5 medium squash)
1 medium yellow onion, finely chopped
2 tablespoons unsalted butter
1/2 teaspoon salt, plus more for seasoning
1/4 teaspoon ground black pepper
1/2 teaspoon garlic powder
1/4 teaspoon ground mustard (optional, but recommended)
1 1/2 cups shredded cheddar cheese (sharp or mild, your preference)
1/2 cup whole milk
1/2 cup sour cream
2 large eggs, beaten
30 buttery crackers (such as Ritz-style), crushed finely (divided use: 20 for filling, 10 for topping)
2 tablespoons unsalted butter, melted (for topping)

Instructions

Preheat your oven to 350°F (175°C) and lightly butter a 9×13-inch baking dish.
In a large skillet over medium heat, melt 2 tablespoons of butter. Add the chopped onion and sauté for about 3–4 minutes, or until translucent.
Stir in the sliced squash and sprinkle with 1/2 teaspoon salt. Cook for 8–10 minutes, stirring often, until the squash is softened and some moisture has cooked off. Remove from heat and let cool for 5 minutes.
In a large mixing bowl, whisk together the milk, sour cream, and eggs. Stir in garlic powder, black pepper, and ground mustard (if using).
Fold in the sautéed squash and onions, 1 1/2 cups shredded cheddar, and 20 crushed crackers. Stir gently until well combined.
Pour the mixture evenly into the prepared baking dish and smooth the top.
In a small bowl, combine the remaining 10 crushed crackers with 2 tablespoons melted butter. Stir to coat completely, then sprinkle evenly over the casserole.
Bake uncovered for 40–45 minutes, or until the top is golden brown and the edges are bubbling slightly.
Let it rest for 10 minutes before serving, to allow the casserole to fully set and slice cleanly.

Can I Use Frozen Or Pre-Cut Squash Instead Of Fresh?

Yes, you can, but there are a few things to keep in mind for the right texture.

Frozen squash releases more water: Always thaw completely and press out extra moisture with a clean kitchen towel or paper towels before using. Too much liquid will make the casserole soggy.
Pre-cut squash saves time: You can use store-bought sliced squash, but check for freshness. If it looks too soft or watery, sauté a little longer during cooking to reduce moisture.
Adjust cooking time if needed: If your squash is very thin or has been frozen before, it might soften faster during the stovetop step.

What Can I Use Instead Of Crackers For The Topping?

If you want a substitute or don’t have buttery crackers on hand, there are plenty of tasty options.

Panko breadcrumbs: These make the top lighter and crispier. Mix with melted butter before sprinkling.
Crushed plain cornflakes: Adds a fun crunch and a slightly sweet note.
Toasted breadcrumbs: Homemade or store-bought, just toast lightly and combine with butter before topping.
Crushed pretzels: Adds a salty crunch if you like a stronger flavor contrast.
Torn stale bread: Tear into small bits, toss in butter, and bake for a rustic topping.

Can I Make This Squash Casserole Recipe Ahead Of Time?

Yes, it’s a great dish to prepare ahead, especially for busy days or gatherings.

Make the full casserole ahead: You can assemble the entire dish (without baking), cover tightly, and refrigerate up to 24 hours. Add the topping just before baking so it stays crisp.
Bake and reheat later: Bake the casserole fully, let it cool, and refrigerate. Reheat covered with foil in the oven at 325°F until warmed through, about 20–25 minutes.
Freeze for future use: Wrap tightly in two layers (plastic wrap and foil). Freeze for up to 2 months. Thaw in the fridge overnight and bake as usual.

How Do I Store Leftover Squash Casserole?

Proper storage helps keep the taste and texture just right for the next few days.

Refrigerate leftovers promptly: Once the casserole has cooled to room temperature, transfer it to an airtight container or cover the dish with foil. Store in the fridge for up to 3 days.
Reheat in the oven or microwave: Use the oven if you want to keep the topping crisp—bake uncovered at 325°F until hot. For a quicker method, microwave individual portions in short bursts until warmed through.
Avoid freezing leftovers: While the baked casserole can technically be frozen, the texture of squash and the topping may become soft or watery after thawing. It’s better to freeze before baking, not after.

What Main Dishes Go Well With Squash Casserole?

This casserole pairs well with a variety of meals, especially during gatherings or large dinners.

Roasted chicken: Its simple flavor lets the casserole shine.
Grilled lamb or beef: Adds richness and depth alongside the creamy, mild squash.
Barbecue dishes: The sweet and smoky flavors of BBQ ribs or pulled meat complement the cheesy casserole well.
Holiday mains: Serve next to baked turkey, glazed ham, or herb-stuffed poultry for festive meals.
Simple salads or soups: If you’re going meat-free, a green salad with vinaigrette or a bowl of tomato soup balances the richness.

Can I Add Extra Vegetables Or Mix-Ins To This Recipe?

Yes, you can customize it with other ingredients, just don’t overdo it or it may affect the texture.

Diced bell peppers: Add a little color and sweetness.
Fresh corn kernels: Give a bit of crunch and a touch of sweetness.
Spinach or kale: Sauté briefly before adding to avoid excess moisture.
Cooked bacon or turkey sausage: For extra flavor and protein.
Shredded carrots or zucchini: Use a light hand and squeeze out moisture well before mixing in.

What’s The Best Way To Get The Perfect Texture?

Getting a good balance of creamy and crispy takes a few key steps.

Sauté squash until moisture reduces: This prevents the casserole from becoming watery.
Don’t skip the cheese and eggs: They help hold the filling together and add richness.
Use the right cracker-to-butter ratio: Too little butter makes the topping dry, too much makes it greasy. Stick to the recipe for best results.
Let it rest before cutting: After baking, give it 10 minutes to settle. This helps it slice neatly without falling apart.

Is This Dish Good For Holidays And Gatherings?

It absolutely is. It’s warm, familiar, and loved by all ages, making it ideal for large meals.

Feeds a crowd: One 9×13 dish easily serves 8, and it can be doubled for more guests.
Prepares ahead: This saves time on the day of the event.
Reheats well: Keeps its flavor and texture for second servings.
Pairs with many sides and mains: Fits easily into most menus without clashing flavors.