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Vegetarian Spaghetti Squash Casserole

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A hearty, cheesy vegetarian casserole made with tender spaghetti squash, colorful vegetables, savory marinara, Italian herbs, and melted cheese. It delivers all the comfort of a baked pasta casserole with plenty of vegetables in every serving.

Ingredients

  • 1 large spaghetti squash
  • 2 tablespoons olive oil, divided
  • 1 medium yellow onion, chopped
  • 3 cloves garlic, minced
  • 1 red bell pepper, chopped
  • 1 medium zucchini, chopped
  • 2 cups baby spinach
  • 3 cups marinara sauce
  • 1 teaspoon Italian seasoning
  • 1/2 teaspoon dried oregano
  • 1/2 teaspoon salt, plus more for seasoning the squash
  • 1/4 teaspoon black pepper, plus more for seasoning the squash
  • 1 cup ricotta cheese
  • 2 cups shredded mozzarella cheese, divided
  • 1/2 cup grated Parmesan cheese, divided
  • Fresh basil or parsley, for serving
  • Red pepper flakes, optional

Instructions

  1. Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
  2. Carefully cut the spaghetti squash in half lengthwise and scoop out the seeds. Drizzle the cut sides with some of the olive oil and season with salt and black pepper.
  3. Place the squash cut-side down on the prepared baking sheet and roast for 35–45 minutes, or until the flesh can easily be pierced with a fork and pulled into strands.
  4. While the squash roasts, heat the remaining olive oil in a large skillet over medium heat. Add the onion and red bell pepper and cook until they begin to soften.
  5. Add the zucchini and garlic and cook for a few more minutes. Stir in the spinach and cook just until wilted.
  6. Add the marinara sauce, Italian seasoning, oregano, salt, black pepper, and optional red pepper flakes. Simmer briefly to combine the flavors.
  7. When the roasted squash is cool enough to handle, scrape the flesh with a fork to create spaghetti-like strands. Drain briefly if the strands contain excess moisture.
  8. Combine the spaghetti squash strands with the vegetable and marinara mixture. Gently stir in the ricotta, 1 cup of mozzarella, and 1/4 cup of Parmesan.
  9. Transfer the mixture to a lightly greased casserole dish and spread evenly. Sprinkle the remaining 1 cup mozzarella and 1/4 cup Parmesan over the top.
  10. Bake for 20–25 minutes, until the casserole is hot and bubbling and the cheese is melted. For a golden top, broil briefly at the end while watching carefully.
  11. Let the casserole rest for 5–10 minutes before serving. Garnish with fresh basil or parsley.

Notes

  • Add drained chickpeas, cannellini beans, or cooked lentils for extra plant-based protein.
  • Mushrooms, broccoli, kale, eggplant, and artichoke hearts can be added for additional vegetables. Cook moisture-rich vegetables before assembling the casserole.
  • Cottage cheese can replace the ricotta, and provolone can be used alongside the mozzarella.
  • For a vegan version, use dairy-free ricotta, mozzarella, and Parmesan alternatives and check that the marinara is vegan.
  • Avoid overcooking the spaghetti squash and drain particularly moist strands before assembling to prevent a watery casserole.
  • The casserole can be assembled ahead, covered, and refrigerated until ready to bake. Add a few extra minutes of baking time when cooking it directly from the refrigerator.
  • Store leftovers in an airtight container in the refrigerator for 3–4 days. Reheat individual portions in the microwave or cover and warm larger portions at 350°F (175°C).
  • Individual portions can be frozen in airtight freezer-safe containers. Thaw overnight in the refrigerator before reheating.

Nutrition

Find it online: https://thefamilycooking.com/vegetarian-spaghetti-squash-casserole/