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Vegetarian Spaghetti Squash Casserole Recipe

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★★★★★

5 from 144 reviews

This Vegetarian Spaghetti Squash Casserole is a flavorful and healthy dish featuring roasted spaghetti squash strands mixed with sautéed vegetables, creamy ricotta and parmesan cheese, layered with tangy spaghetti sauce and melted mozzarella. It’s an easy-to-make, gluten-free casserole perfect for a comforting family dinner or meal prep.

Ingredients

Scale

Squash and Vegetables

  • 1 large spaghetti squash (approx. 3 lbs)
  • 1–2 tsp olive oil
  • 1/2 cup onion, chopped
  • 1–2 cloves garlic, smashed and minced
  • 5 oz mushrooms (2 cups chopped)
  • 2–3 oz fresh spinach (1.5 cups chopped)
  • 1 plum tomato, chopped

Cheese and Seasonings

  • 1.5 cups ricotta cheese
  • 1 egg white (optional)
  • 2/3 cup freshly grated parmesan cheese
  • 1–2 tsp Italian seasoning blend
  • 1/2 tsp dried basil
  • 1/2 tsp garlic powder
  • Salt and pepper, to taste

Toppings and Garnish

  • 1/2 cup spaghetti sauce
  • 2 oz grated mozzarella cheese
  • 1/4 tsp crushed red pepper flakes (optional)
  • 1 tbsp chopped parsley (optional garnish)

Instructions

  1. Preheat Oven: Preheat your oven to 400 degrees F to prepare for roasting the spaghetti squash.
  2. Prepare Squash: Slice the spaghetti squash in half lengthwise and scoop out the seeds. To make cutting easier, poke holes in the squash and microwave whole for 4-5 minutes to soften slightly, allowing the knife to slide through more easily.
  3. Roast Squash: Rub the cut sides of the squash with a small amount of olive oil. Place the halves cut-side down on a lipped baking sheet and roast for about 40 minutes or until tender and easily pierced with a fork. Cooking time may vary depending on squash size.
  4. Prep Veggies and Cheese: While the squash roasts, chop the onion, garlic, mushrooms, spinach, and tomato separately. Set aside your cheeses—ricotta, parmesan, and mozzarella.
  5. Sauté Vegetables: Heat a drizzle of olive oil in a pan or skillet over medium-high heat. Sauté onions until tender and slightly golden. Add garlic and mushrooms, continuing to cook until softened. Drain any excess moisture and set aside.
  6. Mix Cheese Filling: In a large bowl, combine ricotta, egg white (if using), parmesan cheese, chopped spinach, Italian seasoning, dried basil, and garlic powder. Add the sautéed vegetables and chopped tomato. Season with salt and pepper to taste, then mix well.
  7. Separate Squash Strands: Once the squash is roasted and cool enough to handle, use a fork to scrape and separate the squash flesh into spaghetti-like strands.
  8. Assemble Casserole: Lightly grease a baking dish with olive oil. Add the spaghetti squash strands and top with the cheese and vegetable mixture, stirring to combine evenly.
  9. Add Sauce and Cheese: Spread a layer of spaghetti sauce over the squash mixture. Sprinkle the grated mozzarella cheese over the top and optionally add crushed red pepper flakes for a bit of heat.
  10. Bake Casserole: Bake the casserole in a 350 degrees F oven for approximately 20-25 minutes, or until hot and bubbly throughout.
  11. Broil for Finish: For a golden, bubbling mozzarella topping, switch the oven to broil on HIGH and broil for 2 minutes. Watch carefully to prevent burning and remove once bubbling and slightly browned.
  12. Garnish and Serve: Garnish with chopped parsley if desired. Serve the casserole piping hot with a side salad or roasted vegetables for a balanced and satisfying meal.

Notes

  • Microwaving the squash before slicing makes cutting easier and safer.
  • Egg white in the cheese mixture is optional; omit if keeping the recipe fully vegetarian but not vegan.
  • Adjust red pepper flakes to your preferred spice tolerance or omit for no heat.
  • Use fresh herbs for garnish when available for enhanced flavor and presentation.
  • This casserole can be prepared ahead and refrigerated before baking for convenience.
  • Leftovers can be refrigerated for up to 3 days and reheated in the oven.

Keywords: vegetarian casserole, spaghetti squash recipe, healthy casserole, baked spaghetti squash, ricotta casserole, meatless dinner

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