Spaghetti Squash Casserole

This Spaghetti Squash Casserole is one of my favorite vegetarian casserole recipes! Healthy and flavorful, it’s naturally gluten-free and so easy to make vegan.

Spaghetti squash casserole is here to make your vegetarian casserole dreams come true.

I cooke a lot of vegetarian food, and I’ll be honest, casseroles are one of the hardest things to make meatless. This one is special because it combines the heartiness of spaghetti squash with even more veggies and a bit of cheese to create something scoopable and main dish worthy.

This spaghetti squash casserole is a great little detox when you’re regretting eating too many chocolate covered pretzels or light dinner if you’re planning a trip to pilates and don’t want to feel all bloated when you’re trying to sit up without lifting your legs (seriously, try it, it’s impossible… for me).

Spaghetti squash casserole ingredients

Spaghetti squash
Olive oil
Onion
Mushrooms
Garlic
Diced tomatoes
Salt & pepper
Oregano
Thyme
Mozzarella cheese
Parsley

How to make spaghetti squash casserole

Rub the cut side of the squash lightly with olive oil and season with salt and pepper. Place both halves cut side up on a rimmed baking sheet and bake at 400ºF until tender when pierced with a fork, 50-60 minutes.
Remove from the oven and allow to cool slightly before scraping the insides of the squash with a fork to remove the stringy flesh. Place the squash “noodles” in a large bowl and set aside.
While you’re waiting for the squash to cool, heat olive oil in a large pan over medium heat. Once hot, add the onions and cook, stirring frequently, until beginning to soften, 3-4 minutes. Add the mushrooms and cook, stirring frequently, 5 minutes more. Add the garlic and cook, stirring, until fragrant, about 1 minute. Season with salt and pepper.
Add the onion mixture to the squash along with the tomatoes, oregano, and thyme. Stir thoroughly to combine.
Transfer the mixture to an 8×8 baking dish coated with cooking spray and sprinkle with cheese. Bake 30 minutes or until cheese is melted and it is hot throughout. Garnish with chopped parsley if desired and serve.

Spaghetti squash casserole in a glass pan on a wood background.

Top tips

How to cut a spaghetti squash

I like to cut my squash in half from top to bottom with a big, sharp knife. You can check out It’s a Veg World After All for more tips on how to cut a spaghetti squash. There is no need to cut it any smaller than in half for this recipe.

Drain the tomatoes

Don’t forget to drain the tomatoes of the juice they’re canned in. Adding the extra juice will make the casserole too watery. I like to cut off the lid of the can and then hold it in place while tipping it over the sink to drain the liquid.

Doubling the recipe

This recipe makes six servings, but if you’re making it for a holiday you may want to double it. This is easy to do with the servings slider in the recipe card below.

A bite of spaghetti squash casserole on a fork, with more in the background.

Tips for customizing

Add cooked, shredded chicken for meat eaters
Leave off the cheese to make it vegan
Add a diced bell pepper with the onion
Swap the mushrooms for zucchini, halved and cut into disks

FAQ

What does spaghetti squash taste like?

While spaghetti squash doesn’t taste exactly like spaghetti, it does have a bland taste that pairs well with other flavors like those you’ll find in this recipe. It tastes similar to other mild squash such as zucchini.

Is spaghetti squash better for you than pasta?

I believe in most things in moderation, but it’s pretty clear that spaghetti squash is more nutritious than ordinary pasta. It’s high in fiber and lower in carbs and calories than pasta. You’ll also get lots of vitamin C, vitamin B6, and betacarotene.
With all those nutritional benefits, there’s no arguing that this is a healthy vegetarian casserole. Just add an easy vegan salad and you have a full meal!

Can I serve spaghetti squash casserole at Thanksgiving?

This easy squash casserole is vegetarian, gluten-free, and easily made vegan by leaving off the cheese, making it ideal for serving to guests with a variety of dietary needs. I think it makes a tasty addition to any vegetarian (or, altered, vegan) Thanksgiving spread, and could even serve as the main dish. It would also be a great side dish for meat eaters.

How do you keep squash casserole from getting watery?

The casserole can get a little watery as the squash bakes the second time, but I don’t mind it because it keeps the squash soft (I hate crunchy squash!). If you don’t like the extra moisture in your squash casserole recipe, simply squeeze and drain the spaghetti squash after shredding it, before adding it to the other ingredients.

More delicious vegetarian recipes

Spaghetti squash casserole on a white plate against a wood background.

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Spaghetti Squash Casserole

Spaghetti squash casserole ingredients

How to make spaghetti squash casserole