This easy, creamy, cheesy spaghetti squash casserole is full of comfort and is a perfect vegetarian dinner for a family dinner, or as a side dish for steak or chicken. There are three kinds of cheese, peppers, onion and a big helping of spinach tucked into this delicious casserole.
This dish can also be made ahead, covered and refrigerated, as it reheats beautifully in the oven or microwave.
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Vegetarian casseroles are a fabulous dinner solution for families with both vegetarians and meat eaters at the table. They work double duty as a main dish for the vegetarians, and a side dish for the others, like this Broccoli Cheddar Casserole with Quinoa and Yogurt.
And, if you're looking for a Meatless Monday dinner for everyone, this dish is a winner with its cheesy creaminess. And if you're looking to cut back on carbs, the spaghetti squash is a perfect answer.
โค๏ธ Why you'll love this recipe
- Comfort food. Totally checks the comfort food box.
- Make ahead. Make it ahead and warm it back up on busy nights.
- Flexible. Serve it as a vegetarian main dish, add chicken to the casserole for meat eaters at the table, or serve it as a side dish.
- Kid-friendly!
๐ง Main Ingredients + Notes
This list only covers ingredients that require some notes. Go to the Recipe Card at the bottom of this post for a complete listing of the ingredients, measurements, and directions.
- Spaghetti squash - either get one 3-pound or two 1 ยฝ-pound squash.
- Peppers - I used a combination of red bell pepper and poblano chile pepper for a little heat, but you can just use red bell peppers if that's your preference.
- Yellow onion - white onion works well in this recipe too, but red onion is too sweet.
- Baby spinach - I used pre-washed baby spinach in a plastic container to make it super easy. If you use more mature spinach, I recommend you slice off the leggy stems, and coarsely chop before adding to the casserole.
- Cheeses - cream cheese is mixed into the casserole, and a mixture of mozzarella and Parmesan cheese tops the casserole. I used mozzarella cheese in a large round package, that was pre-sliced. This eliminated any cheese grating.
๐ Instructions Overview
Detailed instructions for making this creamy spaghetti squash casserole are in the recipe card below, but here's a quick overview!
Step 1
Spaghetti squash. There are a number of ways to cook spaghetti squash whether you prefer to use your Instant Pot, microwave, oven or air fryer. This post on Air Fryer Spaghetti Squash explains how to cook spaghetti squash in the air fryer with photos for each step. I prefer the air fryer because, hello, it's done in 15 minutes.
Step 2
Sautรฉ. Cook the onion and peppers until softened. Add the garlic and spinach.
Step 3
Melt and fold. Melt the cream cheese into the veggies, and fold in the spaghetti squash "noodles". A wooden spoon is a great way to do this.
Step 4
Fill a baking dish and bake. Pile the spaghetti squash casserole filling into a baking dish. Top with mozzarella and Parmesan cheese. Bake until bubbly.
Step 5
Serve. If you wait about 10 minutes to cut into the casserole, it's easier to slice into portions. Serve warm.
โฐ Tips to Simplify and Save Time
- Cook the spaghetti squash in advance and store in a sealed plastic bag in the refrigerator for up to 3 days.
- Assemble the casserole ahead, cover with plastic wrap, and store in the refrigerator for up to 2 days. Preheat the oven and bake as instructed, adding additional time if you don't bring the assembled casserole to room temperature before baking.
- Use baby spinach that's available prewashed in plastic cartons in the refrigerated section of your grocery produce department.
- Purchase pre-sliced or pre-grated mozzarella for the topping.
๐กIdeas for Possible Variations
- If you like a little crunch to your casseroles, add toasted breadcrumbs on top.
- Add minced Serrano pepper if you prefer more heat.
- During the summer when fresh corn is available, I slice the kernels off one ear of corn and add them to the casserole filling.
- Add soft tofu for a protein boost.
๐ฅฉ Omnivore Options
- Add cooked sausage or bacon to the mixture before baking the casserole.
- Shredded roast chicken is another great addition to this dish. Depending on how much meat you add to the casserole, you may need to increase the amount of cream cheese for a creamy texture.
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Creamy Spinach and Spaghetti Squash Casserole
Equipment
- Air Fryer (or however you plan to cook the spaghetti squash)
- Wooden spoon
- 8"X8" casserole dish
Ingredients
- 3 lb spaghetti squash or (2) 1ยฝ pound squash
- ยฝ cup diced yellow onion
- 1 red bell pepper, diced
- ยฝ poblano pepper, diced
- 1 clove garlic, minced
- 4 cups baby spinach See Ingredient Notes
- โ -1/4 teaspoon ground nutmeg
- 1 ยฝ teaspoons kosher salt or 1 teaspoon sea salt
- ยฝ teaspoon ground black pepper
- 8 ounces cream cheese, softened
- 1 cup sliced or grated mozzarella cheese
- ยผ cup grated Parmesan cheese
Instructions
- Cook the spaghetti squash. I use my air fryer and follow these directions for cooking the squash. The post also includes instructions for roasting spaghetti squash in the oven.Using a fork, gently shred the pulp from the inside of the squash and set aside.
- Preheat the oven to 375หF to bake the casserole when assembled.
- On top of stove, heat the olive oil in a large skillet over medium heat. Add the onion, red bell pepper, and poblano pepper. Sautรฉ until tender, about 5 minutes. Add the garlic and cook until fragrant, about 1 minute.
- Add the spinach to the skillet and season with the nutmeg, salt, and pepper. Cook and stir the mixture until the spinach is wilted, about 3 minutes.
- Gently stir in the cream cheese in chunks until melted. Add the cooked spaghetti squash and stir until combined.
- Pour the mixture into an 8" X 8" casserole dish and top with the mozzarella and parmesan cheese. Bake at 375 degrees for 30 minutes, or until bubbly and the cheese is lightly browned.
- Remove from the oven to a cooling rack for 10-15 minutes before serving if you want to cut the casserole into squares like a lasagna.
Notes
- Peppers - I used a combination of red bell pepper and poblano chile pepper for a little heat, but you can just use red bell peppers if that's your preference.
- Yellow onion - white onion works well in this recipe too, but red onion is too sweet.
- Baby spinach - I used pre-washed baby spinach in a plastic container to make it super easy. If you use more mature spinach, I recommend you slice off the leggy stems, and coarsely chop before adding to the casserole.
- Cheeses - cream cheese is mixed into the casserole, and a mixture of mozzarella and Parmesan cheese tops the casserole. I used mozzarella cheese in a large round package, that was pre-sliced. This eliminated any cheese grating.
Nutrition
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Michaela Kenkel
I can't wait to share this recipe with my son! He and his wife eat lots of spaghetti squash and are always looking for new ways to fix it!
The Wimpy Vegetarian
So am I!! I think he'll love this one!
Tristin
I love that this casserole has spinach and squash! My whole family is going to love this one.
The Wimpy Vegetarian
My husband and I argued over who got the last helping! We all loved it!
Sam
I'm always looking for cozy vegetarian dishes for cold winter nights and this is just perfect!
Kathleen
Love this, made it last night. So bright, fresh and filling -- thanks!
Erin
This combination of flavors is SO GOOD! My family loved them, and this was such a comforting dish for the whole fam.
Sheila
Susan, so glad your family enjoyed my spaghetti squash recipe! It continues to be one of my most popular, and it really is so, so good! Also, thanks for all your kind words ๐
jennifer
spaghetti squash is so versatile and amazing! I can't believe I haven't made more things with it. This recipe is definitely a jumping off point to start experimenting for sure. I loved how creamy it was and the spinach went nicely with the flavor of the squash.
jill
I'm on a big spaghetti squash kick right now and I can't wait to try this recipe! It sounds so good!
Susannah Brinkley Henry
I am always looking for vegetarian recipes that I can serve my vegetarian family members and this one did not disappoint! I can always count on your site to have great recipes for them (that I love too!)
Amy
Such a wonderful dish! I love the small but not insignificant addition of nutmeg! It adds so much complexity and depth and warmth! It's one of my favorite ingredients!