Spaghetti Squash Casserole With Ground Beef and Cheese

Spaghetti squash casserole takes about 1 hour and 30 minutes from oven on to first bite, and most of that is the squash roasting by itself. You get a layered bake of beef and tomato sauce, squash strands standing in for pasta, and a full 2 cups of mozzarella melted on top.

The one thing that decides whether this works is water. Spaghetti squash holds a lot of it, so roast it cut side down and let the strands drain a little before they meet the sauce. Skip that and you end up with a soupy dish.

You brown the beef in a large pot or Dutch oven, build a fast tomato sauce, fold in the squash, then bake it all in a 9 x 13-inch dish. Six generous servings.

Step-by-Step Instructions

1. Heat the oven and prep the dish

Set the oven to 400°F (200°C). Coat a 9 x 13-inch baking dish with nonstick spray and set it aside. The squash goes in first, so the dish just needs to be ready.

2. Halve and seed the squash

Cut the spaghetti squash in half lengthwise on a cutting board. Scoop out the seeds with a spoon and throw them away. Brush 1 tablespoon of the olive oil over both cut faces.

3. Roast cut side down

Place the halves cut side down on a rimmed baking sheet. Bake until a fork slides through the skin with no resistance, about 1 hour. Let them sit for 5 minutes, then rake a fork through the flesh to pull out the strands into a bowl.

4. Soften the onion

Pour the last tablespoon of olive oil into a large pot or Dutch oven and set it over medium-high heat. When the oil shimmers, add the diced onion and cook until soft and lightly golden, about 5 minutes.

5. Add garlic and pepper flakes

Stir in the minced garlic and the red pepper flakes. Keep the spoon moving for about 1 minute, just until you can smell the garlic. Don't walk away, garlic scorches fast.

6. Brown the beef

Add the ground beef and break it apart with a wooden spoon. Cook until no pink is left, about 5 minutes. Stir in the tomato paste and cook for 1 minute more, until it darkens slightly and coats the meat.

7. Build the sauce

Pour in the diced tomatoes with their juice, then add the kosher salt and black pepper. Stir everything together, bring it to a simmer, put the lid on, and cook for 5 minutes. Fold in the squash strands until evenly coated.

8. Fill the dish and top with cheese

Spoon the mixture into the prepared baking dish and spread it into one even layer. Scatter the 2 cups of mozzarella over the top, right to the edges.

9. Bake until golden

Bake until the cheese has melted and turned golden brown in spots, about 20 minutes. Pull the dish out and let it rest for 5 minutes so it slices cleanly.

10. Finish with basil

Scatter the basil over the top and serve. Tear the leaves if they're large.

Tips & Tricks

• Roast the squash cut side down on a rimmed baking sheet. The cut face steams against the pan and the strands come out looser.
• Let the pulled squash strands sit in a colander for a few minutes while the sauce cooks. Any water that drips off is water that won't thin your casserole.
• Break the beef up as it browns. Big clumps make the casserole hard to portion and leave pockets without sauce.
• Spread the mixture flat in the dish before adding cheese. An even layer browns at the same rate all over.

Variations

• Swap the ground beef for ground turkey or Italian sausage. Cook sausage until it reaches 165°F (74°C) on a food thermometer.
• Stir 1 teaspoon of Italian seasoning into the sauce with the tomatoes for a more herbal flavor.
• Use half mozzarella and half provolone for a sharper, stretchier top.

How to Store Spaghetti Squash Casserole

Frequently Asked Questions

Spaghetti Squash Casserole With Ground Beef and Cheese

Tender spaghetti squash strands baked with a quick beef and tomato sauce under a blanket of melted mozzarella. A hearty, low-carb dinner for six.

15 minPrep time80 minCook time100 minTotal6Servings

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Ingredients

• nonstick cooking spray (for greasing)
• 1 medium spaghetti squash
• 2 tablespoons olive oil (divided)
• 1 medium yellow onion (diced)
• 2 cloves garlic (minced)
• ½ teaspoon red pepper flakes
• 1 lb ground beef
• ¼ cup tomato paste
• 1 can tomato (diced)
• 2 teaspoons kosher salt
• 1 teaspoon freshly ground black pepper
• 2 cups shredded mozzarella cheese
• ½ cup fresh basil leaf (for serving)

Instructions

1. 1Heat the oven and prep the dish — Set the oven to 400°F (200°C). Coat a 9 x 13-inch baking dish with nonstick spray and set it aside. The squash goes in first, so the dish just needs to be ready.
2. 2Halve and seed the squash — Cut the spaghetti squash in half lengthwise on a cutting board. Scoop out the seeds with a spoon and throw them away. Brush 1 tablespoon of the olive oil over both cut faces.
3. 3Roast cut side down — Place the halves cut side down on a rimmed baking sheet. Bake until a fork slides through the skin with no resistance, about 1 hour. Let them sit for 5 minutes, then rake a fork through the flesh to pull out the strands into a bowl.
4. 4Soften the onion — Pour the last tablespoon of olive oil into a large pot or Dutch oven and set it over medium-high heat. When the oil shimmers, add the diced onion and cook until soft and lightly golden, about 5 minutes.
5. 5Add garlic and pepper flakes — Stir in the minced garlic and the red pepper flakes. Keep the spoon moving for about 1 minute, just until you can smell the garlic. Don't walk away, garlic scorches fast.
6. 6Brown the beef — Add the ground beef and break it apart with a wooden spoon. Cook until no pink is left, about 5 minutes. Stir in the tomato paste and cook for 1 minute more, until it darkens slightly and coats the meat.
7. 7Build the sauce — Pour in the diced tomatoes with their juice, then add the kosher salt and black pepper. Stir everything together, bring it to a simmer, put the lid on, and cook for 5 minutes. Fold in the squash strands until evenly coated.
8. 8Fill the dish and top with cheese — Spoon the mixture into the prepared baking dish and spread it into one even layer. Scatter the 2 cups of mozzarella over the top, right to the edges.
9. 9Bake until golden — Bake until the cheese has melted and turned golden brown in spots, about 20 minutes. Pull the dish out and let it rest for 5 minutes so it slices cleanly.
10. 10Finish with basil — Scatter the basil over the top and serve. Tear the leaves if they're large.

Cook's note: Let the baked casserole rest 5 minutes before serving so it holds together on the plate. One substitution note: if you don't have tomato paste, use ½ cup of extra tomato sauce and simmer the mixture a few minutes longer to thicken it.

Servings: 6

Cuisine: American

Course: Main Course

RecipesCooker15 minutes80 minutes100 minutes

Written by Maya Whitfield
Maya writes about easy American cookies and bars, plus eggs and breakfast casseroles for busy mornings. She focuses on pantry-friendly ingredients, reliable bake times, and make-ahead steps that fit real weekday schedules. Her recipes keep instructions short and checkpoints clear so nothing gets overbaked or underdone.