Spaghetti Squash Casserole
Ingredients
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- 3 tablespoons olive oil
- 1 1/4 teaspoons kosher salt
- 1/2 teaspoons black pepper
- 3 pounds spaghetti squash (~1.5 medium spaghetti squashes)
- 1 pounds Italian sausage – casings removed (~5.5 medium italian sausages)
- 1 cups onion – finely chopped (~1 medium onion)
- 3 cloves garlic – minced
- 1 tablespoons tomato paste
- 28 ounces crushed tomatoes
- 1 teaspoons dried oregano
- 1/2 teaspoons dried basil
- 2 large eggs – beaten
- 1 cups ricotta cheese
- 8 ounces mozzarella cheese – shredded
- 1/2 cups Parmesan cheese – grated
- fresh basil – chopped (for serving)
Instructions
1. Preheat the oven to 400°F. From the olive oil, set aside 1 tablespoon for the squash and 1 teaspoon for greasing the baking dish; reserve the rest for sautéing. In a small bowl, combine the kosher salt and black pepper to season in two additions later.
2. Halve the spaghetti squash lengthwise and scrape out the seeds. Rub the cut sides with the reserved 1 tablespoon oil and season with half of the salt-pepper mixture. Place cut side down on a rimmed sheet pan and roast until the shells yield to pressure and the strands separate easily, 40–50 minutes; cool 10 minutes.
3. Meanwhile, heat a large skillet over medium. Add the Italian sausage and cook, breaking it up, until browned and just cooked through, 6–8 minutes. Add the onion and cook, stirring, until translucent, 4–5 minutes. Stir in the garlic for 30 seconds, then the tomato paste for 1 minute. Add the crushed tomatoes, dried oregano, and dried basil; bring to a simmer and cook, stirring occasionally, 8–10 minutes, then remove from heat.
4. When the squash is cool enough to handle, scrape the flesh into long strands with a fork. Transfer the strands to a colander set over a bowl and press to remove excess moisture; let drain 5–10 minutes. Season the sauce with the remaining salt-pepper mixture.
5. In a large bowl, whisk the eggs, then mix in the ricotta cheese, half of the mozzarella cheese, and half of the Parmesan cheese, reserving the rest for topping. Fold in the drained squash strands and the sausage-tomato sauce until evenly combined.
6. Reduce oven to 375°F. Grease a 9×13-inch baking dish with the reserved 1 teaspoon oil. Spread the mixture in the dish and smooth the top, then sprinkle evenly with the reserved cheeses. Bake until bubbling at the edges and lightly browned on top, 20–25 minutes.
7. Let the casserole rest for 10 minutes to set. Sprinkle with the fresh basil and serve warm.
Spaghetti Squash Casserole is a cozy American bake that turns the tender, noodle-like strands of roasted spaghetti squash into a hearty, bubbling dish. The squash combines with a savory tomato sauce, Italian sausage, and creamy cheeses, giving you the comfort of a baked pasta without the pasta. Expect a balance of sweet squash, tangy tomatoes, and stretchy, golden cheese with a satisfying, sliceable texture.
The dish reflects the broader casserole tradition in the United States, where baked one-pan meals became weeknight staples in the mid-20th century. Spaghetti squash—introduced to American home cooks in the early to mid-1900s—found popularity as a versatile, lower-starch alternative to pasta. Over time, cooks folded it into Italian American flavor profiles and standard casserole techniques, creating a modern classic that’s both familiar and vegetable-forward.