This spaghetti squash casserole pairs strands of tender spaghetti squash with vegetables and meat sauce to create a delicious, low-carb, high-protein meal that serves a crowd.
Whether you’re looking for a way to add more veggies to your diet or want a lighter alternative to pasta, spaghetti squash is a great option. Once baked, this hearty winter squash can be pulled into long pasta-like strands that are filling and full of nutrients.
The combination of baked spaghetti squash and hearty meat sauce, topped with a bit of mozzarella and parmesan, creates a cheesy spaghetti squash casserole that adults and kids of the family can agree on, and it makes great leftovers too!
Why You’ll Love It
- Low Carb – With 35 grams of carbohydrates and 9 grams of fiber per serving, this low-carb casserole is a veggie-filled meal.
- High Protein – The combination of ground beef, mozzarella, and parmesan ensures that this baked spaghetti squash casserole recipe contains over 25 grams of protein per serving.
- Feeds a Crowd – This recipe makes 6 servings and makes great leftovers too.
- Great for Meal Prep – This spaghetti squash casserole keeps well in the fridge and freezer so it’s great for make-ahead meals.
Ingredients and Substitutions
- Spaghetti Squash – To create a noodle-like base for the casserole, add some veggies and lots of fiber.
- Ground Beef – The recipe calls for ground beef, however, you can use ground bison, ground chicken, or ground turkey if preferred.
- Onion and Garlic – To add some flavor and fragrance to the dish. You can use onion powder and garlic powder if preferred, see the notes section of the recipe for details.
- Bell Pepper – To add some vegetables. The recipe calls for a red bell pepper, however, you can use any color you like or have on hand.
- Tomatoes – A mixture of canned tomatoes and tomato paste to make the meat sauce. The recipe calls for a can of crushed tomatoes, however, you can use a jar of tomato sauce or your favorite pasta sauce if you prefer.
- Herbs – A mix of dried basil, oregano, thyme, and red pepper flakes to make an Italian seasoning for the casserole.
- Mozzarella – To add some protein and a cheesy topping.
- Parmesan – To add some more protein and a bit of saltiness.
- Fresh Basil – To add some freshness and color, parsley also works well.
- Salt and Black Pepper – To season the casserole.
To Make it Gluten-Free: No adaptations are needed, this recipe is gluten-free.
To Make it Dairy-Free: Omit the mozzarella and parmesan completely, or use dairy-free versions instead.
How to Make Spaghetti Squash Casserole
- Cook spaghetti squash. Slice the spaghetti squash into rings, place them on a baking sheet, season them with a bit of salt, and bake them in the oven at 400°F for 40 minutes until tender.
- Brown the beef. Warm the olive oil in a large pot, add the ground beef, and cook until lightly browned and no longer pink. Add onion, cook for 3-4 minutes until tender, then add garlic and cook for an additional until fragrant.
- Make the meat sauce. Add the Italian seasonings, basil, oregano, thyme, red pepper flakes, salt, and black pepper, then add the crushed tomatoes and tomato paste and stir to combine. Reduce heat to a simmer and cook until the squash is baked.
- Shred the baked spaghetti squash. Transfer the cooked spaghetti squash rings to a cutting board and, using a fork, pull the spaghetti squash flesh away from the skin to form strands.
- Make the casserole. Transfer the shredded spaghetti squash strands to the meat sauce, stir to combine, then transfer the mixture to a baking dish, spreading it out evenly. Sprinkle the top with the shredded cheese.
- Bake the casserole. Transfer the baking dish to the oven at 400°F and bake for 20 minutes until the cheese is melted, and the casserole is bubbling.
- Serve and enjoy! Once baked, allow the spaghetti squash casserole to cool slightly, and serve it with a sprinkle of fresh basil on top.
You can find the detailed instructions in the recipe card below.
Red’s Nutrition Tip
While this is a low-carb recipe, I want to be clear that whole-food carbohydrates are nutrient-rich foods and can be included in a healthy diet and even support a goal of weight loss. This low-carb spaghetti squash casserole is just a fun way to add more veggies to the diet and can be served with some crusty bread on the side if you want to increase the carbohydrate content of the meal.
Cut the spaghetti squash into rings. Although you can cut spaghetti squash lengthwise and roast the squash halves, cutting spaghetti squash into rings creates longer strands. Simply place the spaghetti squash on a cutting board horizontally, cut off and discard the stem, then slice the squash into 2-inch-thick rings and bake them in the oven until tender.
Use lean ground beef. Using lean ground beef in this recipe helps to ensure the casserole is not too oily or greasy. In addition to lean ground beef, you can use ground bison, ground turkey, or ground chicken.
Use store-bought sauce. If you want to save time or don’t have a pantry full of herbs and spices, you can use a large jar of your favorite tomato sauce instead of making your own. Just brown the beef and add the sauce to it.
Make it ahead of time. You can make this spaghetti squash casserole ahead of time and quickly reheat it before serving. Prepare the casserole fully as per directions and then reheat it in the oven at 350°F for 15-20 minutes until warmed through and the cheese is bubbly.
This baked spaghetti squash casserole is a delicious low-carb and high-protein meal that can certainly be enjoyed on its own, but if you’re looking to stretch the meal into more portions or make it a little heartier, I suggest serving it with:
- Green salad
- Caesar salad
- Steamed broccoli
- Grilled zucchini
- Garlic bread
Storage + Reheating
To Refrigerate: Once cooled, the spaghetti squash casserole can be stored whole in the baking dish by covering the top with plastic wrap or aluminum foil or in an airtight container in the fridge for up to 5 days.
To Freeze: Allow the casserole to cool completely, then cover it tightly with plastic and aluminum foil, or store leftover spaghetti squash casserole in an airtight container and place it in the freezer for up to 3 months.
To Reheat: Thaw the spaghetti squash casserole completely, then reheat it in the oven at 350°F for 10-20 minutes or in the microwave for 1-2 minutes.
More Casserole Recipes:
- Chicken Burrito Casserole
- Stuffed Pepper Casserole
- Butternut Squash Casserole
- Spinach Breakfast Casserole
- Sweet Potato Breakfast Casserole
Spaghetti Squash Casserole
With over 25 grams of protein per serving, this baked spaghetti squash casserole recipe is a healthy, high-protein, low-carb, and low-calorie meal. Plus, it keeps well in the fridge and freezer, which makes it great for meal prep.
- Prep Time: 15 mintues
- Cook Time: 1 hour
- Total Time: 0 hours
- Yield: 6 slices 1x
- Category: Dinner
- Method: Baked
- Cuisine: American
- 2 medium (about 2 pounds each) spaghetti squash
- 2 tablespoons olive oil
- 1 pound ground beef
- 1 onion, diced
- 1 red bell pepper, diced
- 6 cloves garlic, minced
- 1 teaspoon dried basil
- 1 teaspoon dried oregano
- 1/2 teaspoon dried thyme
- 1/4 teaspoon red pepper flakes (optional)
- 1 teaspoon salt
- 1/4 teaspoon black pepper
- 1 jar or can (28-ounce) crushed tomatoes
- 2 tablespoons tomato paste
- 1 cup shredded mozzarella cheese
- 1/4 cup grated parmesan cheese
- Fresh basil, to serve
- Preheat the oven to 400°F, line a large baking sheet with parchment paper, and grab a 9×13-inch baking dish.
- Place the spaghetti squash horizontally on a cutting board, and slice each of them widthwise into 2-inch rings. Once the rings have been cut, use a spoon to remove any seeds.
- Transfer the squash rings to the baking sheet, season them with a bit of salt, and then transfer the baking sheet to the oven for 40 minutes or until the squash is tender.
- While the squash is baking, prepare the meat sauce. In a large pot on medium-high heat, warm the olive oil, then add the ground beef and cook for 4-5 minutes until browned.
- Add the onion to the beef and continue to cook for 2-3 minutes until tender, add the red bell pepper and cook for an additional 1-2 minutes, then add the garlic, basil, oregano, thyme, red pepper flakes, salt, and black pepper, and cook for a final minute until fragrant.
- Add the crushed tomatoes and tomato paste and stir to combine with the ground beef mixture, then reduce the heat to a simmer and continue to cook, uncovered, until the spaghetti squash is ready.
- Once the spaghetti squash is cooked, remove the baking sheet from the oven, and allow it to cool for a few minutes. When the squash is cool enough to handle, using a fork, pull the squash flesh away from the skin to create noodle-like strands.
- Remove the meat sauce from the heat, transfer the spaghetti squash strands to the pot, and gently stir to combine.
- Transfer the ground beef and squash mixture to a 9×13-inch baking dish, spreading it out evenly, then sprinkle the top with mozzarella cheese and parmesan cheese.
- Transfer the baking dish to the oven to bake for 20 minutes, until the cheese is melted and the top is golden brown.
- The spaghetti squash casserole can be served immediately, with a sprinkle of fresh basil on top, or cooled and stored in the fridge for up to 4 days or in the freezer for up to 3 months.
To Use Onion Powder: Omit the onion and add 1 teaspoon of onion powder along with garlic and herbs in step 5.
To Use Garlic Powder: Omit the garlic cloves and use 1 teaspoon of garlic powder.
- Serving Size: 1 slice
- Calories: 373 calories
- Sugar: 17 grams
- Fat: 15 grams
- Carbohydrates: 35 grams
- Fiber: 9 grams
- Protein: 27 grams