Zucchini & Squash Casserole Recipe

Healthy, simple, and fabulous, this Zucchini and Squash Casserole is the best healthy recipe for summer squash! Yellow squash and zucchini are baked in the oven to perfection with a crispy crust made from Parmesan cheese and breadcrumbs. This easy casserole is amazing for summer picnics and potlucks, and makes the perfect side dish for any holiday dinner! 

Simple Summer Squash Casserole

Zucchini and yellow squash are some of the overlooked vegetables that somehow magically reappear during the summer months and at a Thanksgiving dinner table.

I first discovered my love of cooking with this delightful combo when I ended up with enormous bags full of fresh summer produce from a friend.

After making a few batches of this Sautéed Zucchini and Squash, I started to run out of recipe ideas.

It would have been a sin to let all those healthy veggies go bad, so I had to brainstorm a new summer recipe.

Summer squash casserole has always been one of my favorite summertime side dishes. But, it’s usually full of not-so-healthy ingredients like sour cream and Ritz crackers. (I love those buttery crackers, but there’s a time and a place for them.)

This time, I channeled that bounty of produce into a healthier version of the traditional casserole. I decided to transform it into something simple to make, baked in the oven, and a sure-fire family favorite.

And the results were a crispy, flavorful, healthy side dish that held its own against the original recipe. Once you make this classic Southern recipe with fresh yellow squash and zucchini, you’ll wonder where it’s been your whole life.

Ingredients

The ingredients to make this best squash casserole are pretty simple:

• Squash. Feel free to use all yellow summer squash or all zucchini if that’s what you have. However, the alternating colors are what make this casserole so unique and pretty!
• Olive oil. You can also use any other type of healthy oil that does not have a ton of flavor. Avocado, safflower, and sunflower oils will all work equally as well.
• Garlic Powder. You only need a little bit, but it’s the secret ingredient that gives this dish a unique flavor!
• Parmesan cheese. Regular, dairy-filled Parmesan cheese is best. You can also use vegan and dairy-free Parmesan cheese. If necessary, you can sub in another variety, like sharp cheddar cheese, but the result won’t be quite the same.
• Panko Breadcrumbs. You can use regular breadcrumbs or gluten-free breadcrumbs. The taste will be minimally affected. You can substitute with a seasoned breadcrumb mixture, but you will need to make sure to adjust the amount of salt you add
• Parsley. Not absolutely necessary but it makes the casserole really pretty when serving. You can also use fresh thyme or other herbs you love.

How to Make Squash Casserole

Below, you’ll find the simple steps to make this summer squash casserole recipe at home:

Prep the Squash 

To get the Summer squash ready to bake, there are a few things to do.

First, you need to slice the fresh squash into uniform pieces. You can either use a mandolin (if so be very careful with your fingers!), or you can thinly slice them by hand.

You want them to be ¼-inch thick. If they end up thicker, they will need to cook longer. If thinner, it will likely be soggy instead of crisp.

Next, sprinkle salt over all of the sliced squash and let sit for 10 minutes. Then wipe away any excess moisture that forms with a paper towel.

This little trick allows the sliced zucchini and squash to release a large amount of the excess liquid they typically retain. It will help you to get a crispy, and not soggy, casserole.

Layer in the Pan

Layer the zucchini and yellow squash, alternating types, in a 9-inch square baking dish.

Season the Casserole

Lightly season the layered squash with salt and pepper.

Whisk together breadcrumbs, Parmesan cheese, and garlic powder. Then, pour the mixture in an even layer over the zucchini and squash.

Bake in the Oven

Cover the baking dish with aluminum foil and bake in preheated 350°F oven for 30 minutes. It may take a few minutes more if the slices were cut thick, or less time if the squash slices are thin.

Broil for 3-5 minutes. Keep a close eye on it!  The topping will crisp up and turn golden brown quickly.  

Can you freeze squash casserole?

Yes, you can definitely freeze squash casserole. However, be sure to let it cool completely. Then, cover the pan in plastic wrap so little to no air is coming into contact with the casserole. It should keep in the freezer for up to 2 to 3 months.

Can you make summer squash casserole ahead of time?

Yes, it is easy to prep summer squash casserole ahead of time. Follow all directions but wait to bake until you’re ready to serve. Cover tightly with foil or prepare in an airtight container and refrigerate for up to 2 days. Bring to room temperature and bake according to directions.

How do you keep squash casserole from getting watery?

The answer to keeping your casserole from getting watery is to salt before cooking. Squash releases extra moisture while cooking. However, there is a trick to prevent this. After you’ve sliced your squash, sprinkle it with salt, let it sit for about 10 minutes, then blot dry the moisture that the salt drew out. 

Expert Tips and Tricks

• Use a mandolin. This gives you the most precise slices so they all cook at a similar rate.
• Sprinkle first. A little salt will help prevent a soggy mess. Let the salted squash sit, then blot dry. The salt draws out excess moisture.
• Add some flavor. Try out Italian breadcrumbs. Since they’re pre-seasoned and often contain salt, you will have to adjust the other seasoning ingredients.
• Broil it at the end. This gives it a great crunchy topping.
• Use all of one squash. It’s okay to use all zucchini or all yellow squash if that’s what you have.

What to Serve with Squash Casserole?

This dish is an excellent side for healthy family meals. Try one of these recipes alongside it.

For some flavor, try out this Hot Honey Chicken. Or get fancy with Chicken Cordon Bleu.

Skip the potatoes and try this zucchini casserole with Air Fryer Steak or Filet Mignon.

If you’re a seafood lover, go for Panko Crusted Salmon, Lemon Garlic Baked Salmon or Air Fryer Salmon.

Other Squash Recipes

If you like the best yellow squash casserole, make sure to check out these other easy and healthy recipes.

Baked Parmesan Zucchini Fries and Crispy Zucchini Fritters are so good, you’ll forget they’re good for you.

Zucchini Lasagna Roll-Ups are the perfect Italian-style main dish.

Sautéed Zucchini and Squash is a quick and easy side.

And don’t forget to check out How to Make Zucchini Noodles.