Cheesy squash casserole is a classic side dish that’s perfect for using your summer harvest, but also an excellent addition to any holiday meal. With its creamy sauce and toasty breadcrumb topping, it’s always a hit!

Plate of squash casserole with breadcrumb topping

Unlike hashbrown breakfast casserole and green bean casserole, squash casserole can be a little bit tricky. While it’s simple to make, a lot of recipes leave you with a soggy, bland casserole. This squash casserole recipe won’t let you down, friends!

It’s got a beautiful, creamy sauce that’s packed with flavour thanks to the addition of vegan cheese, sour cream, mayo, and herbs. Plus, I have a trick or two to keep the squash from releasing moisture into the sauce and making it watery.

Why You’ll Love This Squash Casserole Recipe

Rich and creamy—not soggy! By cooking the squash in advance and draining out excess moisture, this casserole stays perfectly creamy. A little bit of cornstarch in the sauce helps too!
The perfect blend of herbs and cheese. The addition of thyme adds a pop of flavour and freshness to the dish, while the combination of cheese and creamy sauce adds richness and depth. We’ve got layers of flavour here!
Versatile enough for any occasion. While this casserole is fantastic for using up squash in the summer, it’s got that creamy-cheesy quality everyone loves in a holiday side dish. It’s also easy enough to make for a weeknight!

Overhead view of ingredients for squash casserole

Notes on Ingredients

Scroll down to the recipe card to find the ingredient quantities and recipe instructions.

Olive oil
Summer squash – Yellow summer squash is the classic choice, but it’s interchangeable with zucchini and heirloom squash. Feel free to use a variety!
Vidalia onion – Or another sweet onion variety, like Walla Walla.
Kosher salt and black pepper
Garlic – For a more garlicky flavour, you can add a second clove.
Thyme – Fresh will give you the best flavour, but if it’s not an option, you can use one-third the amount of dried thyme.
Non-dairy milk – Make sure it’s unflavoured and unsweetened.
Cornstarch
Vegan sour cream – I use store-bought, but you can also use homemade vegan sour cream.
Vegan mayonnaise – Use your go-to store-bought or homemade vegan mayo.
Paprika – I use regular sweet paprika, but smoked paprika would be delicious.
Vegan shredded cheese – Cheddar is my favourite for this recipe, but you can use another variety if you like. Just make sure it’s a good melter!
Vegan butter – Here’s my vegan butter recipe, or use store-bought.
Breadcrumbs – Coarse homemade breadcrumbs are my top choice, but panko is also fantastic. I recommend avoiding the very fine store-bought breadcrumbs, as they don’t add very much flavour or texture.

How to Make Squash Casserole

Overhead view of squash, onions, and thyme in skillet

Overhead view of cornstarch and plant milk in bowl

Prepare. Preheat your oven to 350ºF and coat a casserole dish with cooking spray.
Cook the squash. Add the olive oil to a skillet set over medium heat; once it’s shimmering, add the squash, onion, and salt. Cook until the squash softens, then stir in the garlic and thyme and cook another minute or two.
Drain. Transfer the squash to a colander for 5 to 10 minutes to drain any excess moisture.
Make the sauce. Whisk the non-dairy milk and cornstarch in a large bowl, then whisk in the remaining salt, sour cream, mayonnaise, black pepper and paprika. Fold in the squash and 1/2 cup of cheese.

Overhead view of squash casserole filling in baking dish

Overhead view of squash casserole with cheese on top

Assemble. Transfer the squash mixture to the baking dish. Sprinkle the cheese on top. Stir together the breadcrumbs and melted butter and add that to the top as well.
Bake. Place the baking dish in the oven and bake for 30 minutes, or until the top is golden brown and the sauce is bubbling up along the edges.

Tips and Variations

Drain the squash well. One of the keys to avoiding a soggy casserole is to ensure that your squash is properly drained. Be patient and let it sit in the colander for the full 5 to 10 minutes to remove as much excess moisture as possible.
Use fresh herbs when possible. Fresh herbs provide a much more vibrant flavor compared to dried ones. If you can, opt for fresh thyme.
Swap in a different herb. Rosemary or basil would also be fantastic in this squash casserole.
Get a head start. This casserole can be prepared in advance and baked just before serving. Simply assemble the casserole, cover it tightly, and refrigerate it for up to a day. You can also cook and drain the zucchini and onions in advance and then make the sauce and assemble the next day.
Try another topping. Cornflakes or crushed crackers would make tasty alternatives to the breadcrumb topping.

Top-down view of squash casserole in baking dish with breadcrumb topping

What to Serve With Squash Casserole

I love serving this squash casserole with comfort food dishes like vegan mac and cheese, vegan cornbread muffins, and BBQ tofu. While these recipes are all plant-based, they’ll remind you of the foods you grew up eating!

How to Store Leftovers

Leftover squash casserole can be stored in an airtight container in the refrigerator for up to 3 days. You can reheat it in a 350ºF oven or warm up smaller portions in the microwave.

Overhead view of squash casserole on plate and in casserole dish

Can I Freeze This Recipe?

Yes, this squash casserole freezes well, although do note that it will be a little more watery the second time around. Place it in a freezer-safe container and store it for up to 3 months. Thaw in the refrigerator, then reheat according to the instructions above.

More Vegan Side Dishes

Print Pin

No ratings yet

Squash Casserole

This cheesy squash casserole recipe is a classic side dish with a rich, creamy sauce and toasty breadcrumb topping. It’s always a hit!

Prep Time 10

Cook Time 50

Total Time 1

Servings servings

Calories 383kcal

Ingredients

3 tablespoons olive oil 39 g
3 pounds summer squash cut into 1/4” slices (about 6 squash) 1362 g
1 cup Vidalia onion cut into slices 150 g
1 ½ teaspoon kosher salt divided 9 g
1 clove garlic minced 3 g
2 teaspoons fresh thyme
½ cup non-dairy milk 110 g
2 tablespoons cornstarch 16 g
1 cup vegan sour cream 240 g
½ cup vegan mayonnaise 112 g
½ teaspoon black pepper
¼ teaspoon paprika
¾ cup vegan shredded cheese divided 84 g
3 tablespoons vegan butter melted 42 g
1 cup breadcrumbs 80 g

Instructions

Preheat the oven to 350ºF and spray a 2-quart casserole dish with nonstick cooking spray.
Add the olive oil to a large skillet over medium heat.
Add the sliced squash, onion and 1 teaspoon salt to the oil and cook, stirring frequently, until the squash is barely softened. Add the garlic and thyme and cook 1-2 minutes more.
Remove the squash from heat and place it in a colander to drain any excess moisture. Let it sit for 5-10 minutes.
Add the non-dairy milk and cornstarch to a large bowl. Whisk together until the cornstarch has dissolved.
Add the remaining 1⁄2 teaspoon salt, sour cream, mayonnaise, black pepper and paprika to the milk. Whisk together until it’s a smooth sauce.
Transfer the drained squash to the bowl with the sauce. Add 1⁄2 cup of shredded cheese. Stir everything together.
Spread the vegetables into the prepared baking dish. Cover with remaining shredded cheese.
Combine the breadcrumbs and melted butter and sprinkle them over the top of the casserole.
Bake in the preheated oven for 30 minutes or until the topping is golden brown and the casserole is bubbly.

Notes

To store: Leftover squash casserole can be stored in an airtight container in the refrigerator for up to 3 days. You can reheat it in a 350ºF oven or warm up smaller portions in the microwave.

To freeze: Place the casserole in a freezer-safe container and store it for up to 3 months. Thaw in the refrigerator, then reheat according to the instructions above.

Nutrition