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Mushroom Bolognese Spaghetti Squash Casserole

A gluten-free, lightened version of a delicious casserole made with spaghetti squash and a hearty mushroom bolognese.


  • For The Spaghetti Squash:
  • 1 large spaghetti squash
  • 1 tbsp. olive oil
  • 1/2 tsp. sea salt
  • 1/2 tsp. ground black pepper
  • For The Mushroom Bolognese:
  • 1 tbsp. olive oil
  • 1 yellow onion, diced
  • 10 crimini mushrooms, diced
  • 3 cloves garlic, minced
  • 2 tsp. dried oregano
  • 1 tsp. sea salt
  • 1/4 tsp. ground black pepper
  • 1 28-ounce can crushed tomatoes
  • 6 leaves fresh basil, chopped
  • For The Casserole:
  • 8 oz. fresh mozzarella cheese, sliced


  1. To Make the Spaghetti Squash Noodles:
  2. Preheat oven to 425 degrees F and line a baking sheet with parchment paper.
  3. Slice the squash in half through the stem. Using a spoon, scrape out the seeds and discard.
  4. Drizzle the olive oil over the cut-side of the spaghetti squash, and sprinkle the salt and pepper until evenly coated.
  5. Flip the squash over to be cut-side down on the baking sheet.
  6. Place on the oven and roast until a fork can easily pierce through the skin and flesh, approximately 45 min - 1 hour.
  7. When the squash is cool enough to handle, gently scrape the flesh with a fork to remove it in long strands and then transfer to a medium bowl.
  8. To Make the Mushroom Bolognese:
  9. In a large pan, heat the olive oil over medium-high heat and add the onion. Sauté, stirring frequently, until the onion is softened, about 4-6 minutes.
  10. Add the mushrooms, garlic, oregano, sea salt, and black pepper, and sauté, stirring occasionally, about 3 to 5 minutes.
  11. Add the crushed tomatoes and bring to a boil. Reduce the heat to a simmer, and cook, covered, for 15 minutes.
  12. Remove the lid, and stir in the basil.
  13. Preheat the oven to 400 degrees F and lightly grease a 9-inch square casserole dish.
  14. Transfer the cooked spaghetti squash to the prepared casserole dish, and top with the mushroom bolognese over the noodles. Then, top with the sliced mozzarella.
  15. Place in the oven for 20-25 minutes, or until the cheese is melted and the sauce is bubbling.