Yellow Squash Casserole

Packed full of sweet yellow squash and topped with buttery crackers, this Southern staple is worth turning on the oven, even during the hottest summer days.

A square of yellow squash on a round plate.
Serious Eats / Maureen Celestine

If you’ve ever grown zucchini or yellow summer squash, you know that summertime means one thing: an abundance of the gourd that feels impossible to keep up with. Sometimes all the zucchini bread in the world isn't enough to keep up with it. Enter the yellow squash casserole, a staple side dish of the Southern table that's especially popular at potlucks and holidays like Thanksgiving. Packed full of sweet yellow squash and topped with buttery crackers, it’s a Southern staple worth turning the oven on for, even during the hottest summer days. 

I wish I could tell you that making a yellow squash casserole was as easy as tossing a bunch of ingredients into a casserole dish and baking it. But there’s a little prep work that needs to be done first to ensure you don't end up with flavorless, watery results.

The key to developing the squash's flavor and texture is to first salt it ahead of time to extract excess moisture (more on that below), and then sautée it with aromatics until just tender. Then there’s the creamy base—which comes together quickly in a bowl if you’re working with room-temperature ingredients—and a crunchy topping of crushed Ritz crackers tossed with melted butter and Parmigiano-Reggiano. Once you have all your components, all that’s left to do is assemble and bake.

How to Prevent Yellow Squash Casserole From Becoming Watery

Like its cousin zucchini, yellow squash is almost entirely water! To avoid a mushy, flavorless mess, it helps to first salt the squash, which draws out excess moisture through osmosis. This not only speeds up the cooking process, but also helps to concentrate the squash’s flavor. After a quick dab with paper towels to dry the squash, the squash is pre-cooked in a skillet, helping to further reduce moisture, soften the squash, and develop its inherently sweet flavor.

A square of golden yellow squash casserole.
Serious Eats / Maureen Celestine

Building Flavor: The More Cheeses, the Merrier

Take a look at many squash casserole recipes, and you’ll see that most call for one or more of the following: whole milk, heavy cream, sour cream, cream cheese, or mayonnaise, along with eggs and either grated cheddar or mozzarella cheese. Here, I’ve gone with sour cream and cream cheese, which lends the casserole richness and tang, along with two eggs and a combination of grated cheddar, mozzarella, and, for the topping, Parmigiano-Reggiano. The resulting casserole feels more like your favorite baked macaroni and cheese—except it’s stuffed full of summer squash instead of pasta.

Topping It Off

Here comes the fun part: crushing up Ritz crackers in a zip-top bag with a rolling pin. After you’ve turned the crackers into crumbs, all that’s left to do before baking is a quick toss with melted butter, Parmigiano-Reggiano, and some freshly ground pepper. Sprinkled evenly on top of your squash casserole before baking, the crushed crackers provide a much-needed and satisfying crunch.

Yellow squash casserole in a large rectangular serving dish.
Serious Eats / Maureen Celestine

In a large colander, sprinkle yellow squash with 2 teaspoons kosher salt, tossing to evenly coat. Let stand for 30 minutes, then pat squash dry with paper towels.

Yellow squash salted in a colander.
Serious Eats / Maureen Celestine

Adjust oven rack to middle position and preheat oven to 350ºF (180ºC). Lightly grease a 2 1/2-quart baking dish with unsalted butter and set aside.

A large rectangular serving platter slathered in butter.
Serious Eats / Maureen Celestine

In a 10-inch nonstick pan or cast iron skillet set over medium-low heat, melt 1 tablespoon butter. Add onion and garlic and cook until softened, about 4 minutes. Scrape onto a plate and set aside. Melt remaining 3 tablespoons butter in skillet and, working in batches to avoid crowding the pan, add the squash and cook, stirring to coat in butter, until squash begins to soften around the edges, about 5 minutes. Continue cooking until squash is tender, about 8 minutes. Transfer cooked squash to a bowl and set aside. Repeat with remaining squash, adding 2 tablespoons butter for each additional batch.

Salted yellow squash searing in a pan.
Serious Eats / Maureen Celestine

In a large bowl, whisk together sour cream, eggs, and cream cheese until well-combined. Using a silicone spatula, fold in the cheddar and mozzarella. Drain cooked squash of any pooled liquid, then add to sour cream mixture with reserved onion and garlic. Season to taste with salt and pepper. Pour squash mixture into prepared baking dish and set aside.

Yellow squash and cheese mixture combined in a glass bowl and transferred to a baking dish.
Serious Eats / Maureen Celestine

For the Topping: In a medium bowl, toss crushed Ritz crackers with the melted butter. Stir in the Parmigiano-Reggiano and a few cracks of freshly ground pepper until well combined. Sprinkle cracker mixture over the squash mixture, then bake until golden brown and bubbling, about 1 hour.

Crumbly topping added to yellow squash mixture.
Serious Eats / Maureen Celestine

Special Equipment

Large colander, 2 1/2 quart baking dish, 10-inch sauté pan, silicone spatula

Make-Ahead and Storage

The assembled casserole can be made up until step 5 and kept in the refrigerator for up to two days. When ready to finish, allow the casserole to come to room temperature, top with Ritz mixture, and bake until golden brown and bubbling, about 1 hour.