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Vegetarian Baked Spaghetti Recipe

Vegetarian Baked Spaghetti

Steven
This vegetarian baked spaghetti combines a rich, garlicky tomato sauce with tender spaghetti, sautéed mushrooms and bell peppers for umami depth, and a bubbly golden blanket of mozzarella that stretches with every forkful.
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Prep Time 15 minutes
Cook Time 35 minutes
Total Time 50 minutes
Course Main Course
Cuisine Italian
Servings 8
Calories 520 kcal

Equipment

  • Large pot - for boiling pasta
  • Large skillet or sauté pan
  • 9x13-inch baking dish - or similar size casserole dish
  • Colander - for draining pasta
  • Large mixing bowl
  • Medium mixing bowl
  • Wooden spoon or silicone spatula
  • Sharp knife
  • Cutting board
  • Measuring cups and spoons
  • Cheese grater - for grating Parmesan
  • Aluminum foil - for covering dish while baking

Ingredients
  

  • 12 oz spaghetti - 340g
  • 2 tablespoons olive oil
  • 1 medium yellow onion - about 1 cup or 150g, diced
  • 4 cloves garlic - minced
  • 8 oz cremini or baby bella mushrooms - 225g, sliced
  • 1 medium green bell pepper - diced
  • 1 medium red bell pepper - diced
  • 1 teaspoon dried Italian seasoning
  • 1 teaspoon dried basil
  • 0.5 teaspoon dried oregano
  • 0.5 teaspoon red pepper flakes - optional, for heat
  • Salt - to taste
  • Black pepper - to taste
  • 24 oz marinara sauce - 680g jar, high-quality preferred
  • 1 cup crushed tomatoes - 240ml
  • 15 oz whole-milk ricotta cheese - 425g
  • 1 large egg
  • 0.25 cup fresh Parmesan cheese - 25g, grated, plus more for serving
  • 2 cups shredded mozzarella cheese - 225g, divided
  • 2 tablespoons fresh parsley - chopped, for garnish
  • Fresh basil leaves - optional, for garnish

Instructions
 

  • Preheat oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish with olive oil or cooking spray.
  • Boil spaghetti in salted water 2 minutes less than package directions (until firmly al dente). Reserve ½ cup pasta water, then drain and toss with olive oil to prevent sticking.
  • Sauté onion in olive oil over medium-high heat until soft, 3-4 minutes. Add garlic and cook 30 seconds until fragrant. Add mushrooms and cook undisturbed 2-3 minutes, then continue 5-7 minutes until liquid evaporates.
  • Add bell peppers and cook 3-4 minutes until slightly softened. Season with Italian seasoning, basil, oregano, red pepper flakes, salt, and pepper.
  • Pour marinara sauce and crushed tomatoes into the skillet. Simmer 5 minutes, stirring occasionally, until thickened slightly. Adjust seasoning to taste.
  • Mix ricotta, egg, Parmesan, salt, and pepper in a medium bowl until smooth and well combined.
  • Combine drained spaghetti with two-thirds of the sauce in a large bowl, tossing until fully coated.
  • Spread half the sauced spaghetti into the prepared baking dish. Top with ricotta mixture, then ½ cup mozzarella. Add remaining spaghetti, then spoon remaining sauce over top and sprinkle with remaining 1½ cups mozzarella.
  • Cover with foil and bake 20 minutes. Remove foil and bake 15-20 minutes more until cheese is bubbly and golden at the edges. Broil 2-3 minutes for extra color if desired.
  • Rest 10 minutes before slicing. Garnish with parsley and fresh basil, then serve.

Notes

  • Undercook the pasta: Boil spaghetti 2 full minutes less than package time. It will finish cooking in the oven for the perfect tender-but-not-mushy texture.
  • Don't skip draining the mushrooms: Let mushrooms fully release and cook off their liquid to prevent a watery, diluted sauce in the final dish.
  • Use whole-milk ricotta: Part-skim ricotta can turn grainy and watery when baked. Whole-milk stays creamy and rich.
  • Season every layer: Taste and season the vegetable mixture, ricotta, and pasta as you go for the most flavorful result.
  • Grate your own cheese: Pre-shredded mozzarella contains anti-caking agents that prevent smooth melting. Shred from a block for the best texture.
  • Make ahead option: Assemble the entire casserole up to 24 hours in advance, cover tightly, and refrigerate. Add 5-10 minutes to covered baking time when baking from cold.
  • Freezing instructions: Cut cooled baked spaghetti into individual portions, wrap tightly, and freeze up to 3 months. Thaw overnight in refrigerator before reheating.
  • Variation ideas: Add 2-3 cups fresh spinach or kale to the vegetable mixture, swap bell peppers for zucchini, use cottage cheese instead of ricotta, or try a vodka sauce base.
  • Storage: Leftovers keep in the refrigerator for up to 4 days. Reheat covered with a spoonful of marinara or water to restore moisture.
  • Gluten-free option: Substitute your favorite certified gluten-free spaghetti and follow the recipe as written.
Keyword cheesy spaghetti casserole, easy weeknight dinner, meatless pasta bake, vegetarian baked spaghetti