Easy Summer Squash Casserole for Party or Potluck

Carol Lander
by Carol Lander
8 servings
1 hr 5 min

I love summer vegetables: corn, okra, tomatoes, zucchini and summer squash. When I spied a bunch of summer squash, I knew it was time for a easy summer squash casserole.

This easy summer squash casserole would be perfect to serve for a weeknight or a party for a crowd. There may even be leftovers for the week.

Sweet Shark loves casseroles and asks for them often. If possible, I love to stop by a local Farmers’ Market for farm~grown vegetables.

Casseroles may take time upfront to assemble, but they have the advantage of being made ahead and frozen if you like. I’ve made this summer squash recipe from Southern Living is so easy. I’ve made it several times so I know how delicious it is.

I love its rich and creamy texture and crunchy topping. As usual, I’ve increased the flavor profile with added seasoning ingredients.

Memorial Day may be behind us for this year, but I really wanted to share this delicious recipe with you. 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.

Party or Potluck Easy Summer Squash Casserole

Use your prettiest 11 X 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.

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

Easy Summer Squash Casserole Ingredients

This is the summer squash I bought at the 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 the texture of this casserole so good is the combination of mayonnaise ~ I use Hellman’s ~ and sour cream. 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.

Three types of cheese ~ cheddar and Swiss in the squash mixture and Parmesan in the crunchy topping all contribute to the flavor factor.

The Ritz butter crackers add flavor and texture to the topping. I thought I wanted to divide the summer squash casserole into 2 portions so I got out my square Le Creuset baking dish and a round deep pie dish ~ red and blue.

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 Summer Squash Casserole

Go ahead and preheat your oven to 350˚F.

Step 1 ~ The first step is to dice the onion and slice the squash. 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 tables of unsalted butter in a large skillet, then add the squash and onions. I started using my 10~inch cast iron skillet.

NOTE: To avoid dairy, I would use 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~size 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 and 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.

As you grate the cheddar and Swiss cheeses, again 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, tarragon (Mexican mint marigold), and mint, which are perennials. Basil is the only herb that we have to plant each spring.

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 and set over the bowl for about 5 minutes.

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.

I put the crackers in a Zip~Lock baggie and use my meat mallet to gently crush them. They are so soft, 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 so you don’t mush the squash.

Step 10 ~ Place the mixture in your baking dish and smooth to fill it. Then sprinkle the cracker topping on top, covering all the mixture. I sprinkled a little bit more cayenne on top for flavor and color.

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

NOTE: I only used about 1/2 the topping mixture. I put the rest back in the Zip~Lock baggie I used to crush the crackers and placed it in the fridge. It’s great for sprinkling on top of fish or 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 and delicious. It’s awesome served with any kind of barbecue, fried chicken, baked ham, or brisket.

Cover leftovers ~ if you have any ~ with foil and place 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 200˚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

I hope you try this easy Summer Squash Casserole. Everyone will thank you. Be sure to PIN IT.

Easy Summer Squash Casserole for Party or Potluck
Recipe details
  • 8  servings
  • Prep time: 45 Minutes Cook time: 20 Minutes Total time: 1 hr 5 min
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  • 6 tablespoons unsalted butter divided use
  • 3 pounds summer (yellow) squash from 5 medium squash, ends removed, sliced 1/4~inch thick
  • 1 medium yellow onion medium dice, about 1 1/2 cups
  • 2 teaspoons kosher salt divided use
  • 2 large eggs lightly beaten
  • 1 (8~ounce) carton sour cream
  • 4 ounces sharp Cheddar cheese shredded, about 1 cup
  • 2 ounces Swiss cheese shredded, about 1/2 cup
  • 1/2 cup good quality mayonnaise
  • 2 teaspoons chopped fresh thyme
  • 1/2 teaspoon freshly ground black pepper
  • 2 sleeves round buttery crackers (such as Ritz) coarsely crushed
  • 1 ounce Parmesan cheese shredded (about 1/4 cup)
  • 2 cloves garlic peeled and chopped (optional)
  • 1 teaspoon ground cayenne divided use (optional)

Preheat the oven to 350˚F. Lightly grease an 11 X 7~inch baking dish and set aside.
Melt 3 tablespoons of the unsalted butter in a large skillet over medium~high heat. Add the squash, onion, garlic (if using) and salt and cook, stirring often, until center of squash is just tender the onion is translucent, about 10 minutes.
Transfer mixture to a colander set over a bowl and allow to drain for 5 minutes. Discard any liquid.
In a large bowl, combine the eggs, sour cream, and mayonnaise. Stir in the Cheddar and Swiss cheeses, salt, pepper, and thyme and cayenne (if using. Gently fold in the squash mixture until thoroughly combined.
Transfer mixture to the baking dish and smooth on top.
In a medium bowl, microwave the 3 remaining tablespoons of butter on HIGH for 25 seconds until melted. Add the crushed crackers and Parmesan cheese and toss to combine. Add a pinch of cayenne, if desired. Sprinkle the cracker mixture over the squash mixture, covering it completely. Bake in preheated oven for 20 minutes until golden brown.
Carol Lander
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  • Mai Mai on Jul 09, 2022

    This is delicious! Vegetarian here, so I use as a main dish. In place of cayenne, I tried a little freshly grated nutmeg. Nice flavor for occasional change.