This Spaghetti Squash Casserole is dreamy, healthy vegetarian comfort food!

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.

Spaghetti squash doesn’t taste exactly like regular spaghetti, but when paired with tons of veggies it comes pretty darn close. 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).
This easy squash casserole is vegetarian, gluten-free, and easily made vegan by leaving off the cheese. I think it makes a tasty addition to any vegetarian (or, altered, vegan) Thanksgiving spread.

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.
This spaghetti squash casserole is easily customized! Here are a few ideas to get you started:
- 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
If you like spaghetti squash casserole you may want to try:

If you make this recipe be sure to rate it, leave a comment, or tag #theliveinkitchen on Instagram!


Spaghetti Squash Casserole
Ingredients
- 1 medium spaghetti squash, halved and seeds removed
- 1 tablespoon olive oil, plus more for rubbing the squash
- 1 medium onion, chopped
- 8 ounces baby portobello mushrooms, sliced
- 1 clove garlic, minced
- Coarse kosher salt and freshly ground black pepper
- 14.5 ounce can diced tomatoes, drained of excess liquid
- 1/2 teaspoon dried oregano
- 1/2 teaspoon dried thyme
- 1/2 cup shredded mozzarella cheese
- Chopped fresh parsley, optional
Instructions
- Preheat the oven to 400ºF. Spray an 8×8 baking dish with cooking spray and set aside.
- Rub the cut side of the squash lightly with olive oil and season with salt and pepper. Place both halves cut side up 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 the prepared baking dish 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.
Nicole, RD says
I don’t adore spaghetti squash on its own, but this look FANTASTIC!
Tonia from TheGunnySack says
I love spaghetti squash so I’m going to have to give this a try!
taylor @ greens & chocolate says
I’m on a pretty permanent sugar high as well. I’m trying to keep my meals in between the cookies healthy…this casserole looks perfect for that! Comforting AND healthy!
Rebecca says
About how many servings does this make? It looks awesome.
Maris says
Looks delicious and deceptively healthy!
Lindsay Moe says
Thanks Maris, it totally is!
Cynthia | What A Girl Eats says
We eat a lot of spaghetti squash around here! This sounds perfect for my family!
Lindsay Moe says
Enjoy Cynthia!
Lisa Anne Becker says
I just made this for dinner. It was DELICIOUS!!!! I am new to your site but I will be back again, and again, and again…
Lindsay Moe says
That’s great to hear Lisa, I’m glad you enjoyed it!
Paul says
Lindsay,
Loved the spaghetti squash casserole! Did taste just like spaghetti, and my wife, who’s on Weight Watchers, really appreciated it as well.
Lindsay Moe says
That’s great to hear, glad you enjoyed it!
Pam Allard says
This is one of my go to recipes, thank you! It’s nutritious, delicious and low in calories and carbs.
Lindsay Moe says
I’m so glad you enjoyed it Pam!
Lisa Bixby says
I loved that this was a meatless variation.
I combined the mozzarella with some 6 oz ricotta and made a lasagna style creamy cheesy layer.
Nicole says
Can you freeze leftover casserole?
Lindsay Moe says
Yes, it should freeze well.