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Two stuffed spaghetti squash halves on a baking sheet with parchment paper

Vegetarian Lasagna Stuffed Spaghetti Squash

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  • Author: Alex Aldeborgh
  • Prep Time: 45 minutes
  • Cook Time: 15 minutes
  • Total Time: 1 hour
  • Yield: serves 2
  • Category: main dish
  • Cuisine: Italian
  • Diet: Vegetarian


This vegetarian stuffed spaghetti squash is bursting with lasagna flavor from tomato sauce and ricotta and mozzarella cheeses. Sauteed mushrooms and spinach take the place of meat in this delicious and vegetable-packed main dish.


  • 1 large spaghetti squash
  • 1 tbsp olive oil
  • 1 small white onion, diced
  • 3 cloves garlic, minced
  • 2 1/2 cups sliced baby bella mushrooms
  • Salt
  • Pepper
  • 4 cups baby spinach
  • 1/2 tsp Italian seasoning
  • 1 1/2 cups tomato sauce
  • 1/4 cup fresh basil, chopped
  • 4 oz ricotta cheese
  • 1/2 cup shredded mozzarella cheese


  1. Preheat oven to 400 degrees F. Line a baking sheet with parchment paper.
  2. Cut spaghetti squash in half the long way (see notes for tips). Drizzle the cut sides with olive oil and a pinch of salt and pepper.
  3. Place the squash halves, cut side down, on the baking sheet. Bake in the oven for 30-45 minutes, until you can easily pierce the skin with a fork.
  4. Flip the squashes over using oven mitts to let them cool.
  5. Heat olive oil on medium heat in a saute pan. Add onion and garlic, cooking for 1-2 minutes until fragrant.
  6. Add the sliced mushrooms. Cook for another 5-7 minutes, stirring occasionally, until mushrooms are soft.
  7. Add the spinach and Italian seasoning to the mushrooms, then cook until spinach is wilted. Remove from heat.
  8. Use a fork to scrape out the flesh of the spaghetti squash into noodle-like strands. Put these in a mixing bowl, and reserve the outer shells.
  9. To the same mixing bowl, add the mushroom and spinach mixture, 1 cup of tomato sauce, fresh basil, and a pinch of salt. Mix it all up to combine.
  10. Transfer this mixture  back into the two spaghetti squash shells equally. 
  11. Top each shell with an equal amount of the remaining tomato sauce, ricotta cheese, and shredded mozzarella.
  12. Reduce the oven heat to 375 degrees F. Put the spaghetti squash boats back on the baking sheet and bake in the oven for 15-20 minutes, or until cheese is melted and sauce is starting to bubble.
  13. Top each half with some fresh basil and enjoy!


How to cut spaghetti squash

The outer skin on spaghetti squash is quite tough and hard to cut through. To make it much easier to cut, pierce a few holes in the squash using a fork. Then microwave the whole squash for 3-5 minutes. Then use a sharp knife to cut the squash into two halves the long way.

Storing stuffed spaghetti squash

If you are cooking for yourself, you can store the other spaghetti squash half in the fridge for a day or two after you make it. Store it upright in an airtight container, or on a plate covered with tin foil.

Reheat it in the oven at 300 degrees F for about 20 minutes, until it is hot and cheese is melted.