Summer squash casserole is a fantastic option as a zucchini and squash medley. Definitely not the same old squash casserole you are used to, this casserole side dish is a great way to use up abundant summer gardens.

There is no doubt that vegetable casserole dishes like this yellow squash casserole are visually stunning. As such, they make perfect potluck side dish recipes because they taste as good as they look. When summer squash hits the store, you WILL BE READY.

outstanding summer squash casserole recipe with panko bread topping

Now to be completely frank, this dish isn’t the quickest. Prep on casseroles where vegetables have to be cut and ingredients have to be layered typically take a bit more work. But Southern dishes like this work for a reason and this layered squash casserole is the PERFECT way to celebrate a blooming garden.

And can we talk about the panko crumbs? As a self-proclaimed panko crumb fantastic, the simple yet golden brown panko crust gives this recipe an expensive look with an easy flair.

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Ingredients

This fabulous recipe will require a handful of ingredients that are not always available in personal pantries. Make sure you have the following or can pick up the following before proceeding to the instructions.

Butter
White Onion – Sliced
Salt & Pepper
Minced Garlic
Dried Thyme – you can most certainly use fresh Thyme but its easier in this dish to include the dried
Fresh Basil – that being said, fresh basil is way better than dried so use the fresh here
Dry White Wine – cooking wine is fine
Kalamata Olives – chopped up into small pieces
2 pounds Fresh Zucchini – sliced 1/4th inch rounds
2 pounds Fresh Yellow Squash – sliced 1/4th inch rounds
Panko Bread Crumbs
Grated Parmesan

Yellow Squash Casserole Prep

Before you get started, preheat the oven to 425 and grease a 9×13 baking pan.

Prep Casserole Ingredients

Add 2 tablespoons butter, onions, 1/2 teaspoon salt, and 1/4 teaspoon pepper and heat over medium heat, stirring frequently until onions are soft and browned about 10-12 minutes.

Stir in garlic and thyme and cook for 1 minute.

Stir in wine and cook until evaporated, about 2-3 minutes. Remove from heat and stir in olives. Set aside.

In a small bowl, combine panko bread crumbs, 1 teaspoon ground pepper, and mix well.

summer squash medly with onions, olives and fresh herbs in a cast iron pan

Prep Vegetables

Add zucchini and squash into a large microwave-safe bowl and season with salt and pepper.

The easiest way to do this is to add a layer of zucchini, sprinkle with salt and repeat until the bowl is full. Cover and microwave for 8 minutes, stirring vegetables halfway through.

Carefully drain the dish in a colander (to remove excess moisture) and let cool.

Place a triple layer of paper towels onto a plate and add squash rounds. Put another layer of paper towel on top and gently press the liquid from the squash.

yellow squash and zucchini rounds microwaved and sitting in a bowl

Assemble Casserole

Sprinkle 6 tablespoons of bread crumb mixture onto the bottom of the baking pan.

Melt 4 tablespoons butter and mix with remaining panko mixture.

Arrange half of the zucchini and squash in the baking dish on top of the bread crumbs.

Sprinkle with 1/4 cup panko mixture and top with onion and olive mixture.

Arrange remaining zucchini and squash on top and cover with foil.

Bake casserole for 10 minutes.

Remove foil and discard.

Sprinkle with remaining bread crumbs and return to oven for 10-15 minutes or until golden brown and bubbling around edges.

Let stand for 15 minutes before serving.

Casserole Recipe Questions

Can Squash Casserole be made in advance?

Most casseroles hold up relatively well when assembled in advance. The key to any dish that is prepped and stored in the fridge is the change in temperature of the initial ingredients. Once added to the fridge, food gets extra cold and needs to come up close to room temp prior to oven baking.

If you are going to make this one in advance to store, bring it up to room temp about 30 minutes prior to baking. Additionally, do not add any topping or it will contain too much moisture. Add the final crumb layer just before baking.

What are the best variations or ingredients to add to the casserole to mix it up?

Not everyone is a fan of olives, so that can easily be left out. Additionally, tomatoes go really well with squash and zucchini and can be added between slices. This is done in my zucchini tomato casserole recipe here.

Are there any other toppings that can be used?

Personally, I would always opt for panko crumbs as they hold that delicious crunch so well. But you could always use Ritz Cracker topping as we did in Broccoli Cheese Casserole.

scoops taken out of summer squash casserole

Looking for more spring and summertime casserole recipe suggestions?

Oven Baked Spaghetti Squash – once you learn how to oven bake spaghetti squash, it can be added in a ton of casseroles, eaten right out of the yellow squash boat as a stand alone dish or used as a low carb noodle solution!
Zucchini Bread – if you haven’t tried zucchini bread yet, trust me. Its the summer equivalent of fall favorite pumpkin bread. Moist, delicious and worth the make!
Oven Roasted Butternut Squash – Again, this recipe is a basic skill of learning how to make butternut squash, which can in turn be scooped and used for a variety of recipes – even baby food!
Zucchini Tomato Casserole – if you missed this mention above, this squash casserole version is just SO GOOD and rated highly amongst readers here on Salty Side Dish!

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Ingredients