Easy and Delicious Squash Casserole for a Party or Potluck

I love summer vegetables: corn, okra, tomatoes, zucchini, and summer squash. When they’re in season, we should take full advantage, so when I spied a bunch of summer squash at our local Farmers’ Market, I knew it was time for an easy and delicious summer squash casserole.

This easy squash casserole is perfect for a weeknight dinner or a party side dish for a crowd, like the 4th of July. If you’re lucky, there may even be leftovers for the week. The rich, creamy texture and crunchy topping make it a guaranteed crowd-pleaser.

Although you can prepare this summer squash casserole any time of year, I especially enjoy it in the summer, when squash grows like a weed. It isn’t called summer squash for nothing.

Casseroles may take time to assemble upfront, but they have the advantage of being made ahead and frozen if you like. This summer squash recipe (originally from Southern Living) is so easy, and I’ve made it several times, so I know how delicious it is. As usual, I’ve enhanced the flavor profile with additional seasonings. Sweet Shark loves casseroles and asks for them often, and this one is no exception.

Be sure to save this easy summer squash casserole for your next party, potluck, family dinner or 4th of July celebration. It’s summer in a casserole.

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Party or Potluck Easy Squash Casserole

Use your prettiest 11-by-7-inch baking dish for the summer squash casserole. I used my red oval Le Creuset casserole dish, but here is a very similar blue casserole dish. It comes with a lid for leftover storage.

You could divide the recipe into two square brownie-size baking dishes, like this pretty ceramic one from Le Creuset.

Easy Squash Casserole Ingredients

Obviously, summer squash is first on the list of casserole ingredients.

• I bought this summer squash at our local Farmer’s Market. I love supporting our local farmers, and there is nothing better than homegrown vegetables. Summer squash is abundant already, so you shouldn’t have any trouble finding it.

What makes this casserole’s texture so good is the combination of mayonnaise and sour cream.

• mayonnaise – I use Hellman’s. I don’t recommend Kraft because it’s too sweet.
• sour cream
• cheddar cheese
• Swiss cheese
• Parmigiano Reggiano – for the topping
• Ritz butter crackers – add flavor and texture to the topping
• yellow onion
• garlic cloves
• unsalted butter or olive oil
• kosher salt
• freshly ground black pepper
• ground cayenne (optional)
• fresh chopped

I wanted to divide the summer squash casserole into two portions, so I used my square Le Creuset baking dish and a round deep pie dish – red and blue.

This casserole is not on any diet list. It’s so rich that you don’t have to have a big portion to be satisfied.

In full transparency, I stopped eating dairy over four years ago when I started following a new eating plan. That means no cheese, no dairy, no pasta, no rice, no sugar, no beans, and no legumes. The secret is a daily 8 – 12 ounces of bone broth for breakfast. The result was a 20-pound loss, which is exactly what I wanted. I met my goal back in January of 2022 and have ( sort of) maintained the loss. I do have to admit that I also cheat occasionally.

I do occasionally have a “cheat meal”, which I plan for. Or I may have just a bite or two of something that’s really good, like this summer squash casserole.

NOTE: You can grate the cheeses, crush the crackers, and mix the mayo and sour cream ahead or do it while the squash cooks.

Making the Squash Casserole

Go ahead and preheat your oven to 350˚F.

Step 1 – Dice the onion and slice the squash into 1/4- to 1/2-inch coins. It will seem like a lot, but it does cook down some.

NOTE: In the past, I have added a couple of peeled and chopped garlic cloves for more flavor.

Step 2 – Heat 3 tablespoons of unsalted butter in a large skillet, then add the squash and onions. I use my 10-inch cast-iron skillet.

NOTE: To avoid dairy, I used olive oil instead of butter.

I soon decided the skillet wasn’t big enough to cook the squash mixture. Since you need to stir and turn the vegetables often, you need a really large skillet.

Step 3 – Add a teaspoon or so of kosher salt and cook the vegetables over medium to medium-high heat for at least 10 minutes. I let mine sweat for about 15 minutes. The onion should be translucent and the squash barely soft, but definitely not mushy.

Step 4 – Meanwhile, place your 2 large eggs and sour cream in a large bowl. Add the mayo and whisk until smooth.

TIP: Rather than using a measuring cup to measure the mayo, use the empty sour cream container. It’s 8 ounces, which is 1 cup. Just fill it about 1/2 full.

TIP: As you grate the cheddar and Swiss cheeses, use the sour cream container as a measuring cup. Don’t grate the Parmesan just yet.

Step 5 – Add the cheeses and the chopped thyme to the bowl.

I used thyme from our herb garden. I love having fresh herbs for cooking. We have rosemary, chives, thyme, sage, parsley, tarragon (Mexican mint marigold), and mint, which are perennials. Basil is usually the only herb that we have to plant each spring. Sometimes, we do have to replant our parsley and mint.

NOTE: I like to add a little cayenne for an extra kick – just 1/4 to 1/2 teaspoon, depending on your heat tolerance.  Add the kosher salt and pepper. Now blend everything until smooth.

Step 6 – By now, the squash and onions should be ready. Have a colander and bowl on hand. Drain the squash mixture over the colander, then set the colander over the bowl for about 5 minutes to let the squash drain.

You want as much liquid to drain away from the squash. This will keep the casserole from being watery and cools down the squash.

Step 7 – While the squash is draining, you can grate the Parmesan cheese and crush the Ritz crackers.

TIP: I put the crackers in a Zip-Lock baggie and use my meat mallet to gently crush them. They are so soft that you can probably just use your hands to coarsely crush them.

Step 8 – Add the crushed crackers and grated cheese to the melted butter and toss to combine. I also added a pinch of cayenne to the topping mixture.

Assembling the Squash Casserole

You’re almost finished.

Step 9 – Add the cooled and drained squash/onion mixture to the sour cream/mayo/cheese mixture, gently folding it in with a rubber spatula so you don’t mush the squash.

Step 10 – Place the mixture in your baking dish and smooth it to fill the dish. Then sprinkle the cracker topping on top, covering all the mixture. I sprinkled a little bit more cayenne on top for flavor and color. Sprinkle with chopped thyme, oregano, or parsley, if you like.

TIP: If you want color but not heat, use paprika instead.

NOTE: I only used about 1/2 of the topping mixture. I put the rest back in the Zip-Lock baggie I used to crush the crackers and placed it in the freezer. It’s great for sprinkling over fish, chicken, or vegetables.

Step 11 – Place the casserole in the preheated oven and bake for 20 minutes.

The casserole should be golden brown on top.

The squash casserole is so easy, has a wonderful texture, and is creamy and delicious. It’s awesome served with any kind of barbecue, smoked ribs, fried chicken, baked ham, or brisket.

Cover leftovers – if you have any – with foil and place them in the refrigerator. To reheat, remove from the fridge for 30 minutes. I usually put the casserole in a cold oven and then reheat it at 225˚F.

If you need some more summer recipes, then I have more from my kitchen to yours.

• Summer Creamed Corn
• Oven-Baked Brisket
• Summer White Sangria
• Best Summer Peach Cobbler

Summer Squash FAQ

I hope you try this easy Squash Casserole. Everyone will thank you. Be sure to PIN it to save it. Also, check out these Pinterest Boards full of great summer dishes: Summer Recipes, Summer Party Foods, and Vegetable Recipes