Vegetarian Baked Spaghetti
This vegetarian baked spaghetti is the ultimate meatless comfort food — a hearty, cheesy pasta casserole layered with sautéed zucchini, mushrooms, bell peppers, and onions in a rich garlic tomato sauce, then topped with creamy ricotta, melty mozzarella, and freshly grated Parmesan. It bakes up golden and bubbling, feeds a crowd, and is just as satisfying the next day. Perfect for weeknight dinners, meal prep, or feeding picky eaters who swear they'll miss the meat.
Equipment
- Large pot For boiling pasta
- Colander For draining pasta
- Large skillet or sauté pan For building the vegetable tomato sauce
- 9x13-inch ceramic or glass baking dish For assembling and baking the casserole
- Wooden spoon or spatula For stirring
- Medium mixing bowl For the ricotta mixture
- Chef's knife and cutting board For prepping vegetables
- Measuring cups and spoons
- Aluminum foil For covering the dish while baking
- Box grater For grating Parmesan; optional if using pre-grated
Ingredients
- 12 oz spaghetti 340g
- 2 tbsp olive oil
- 1 yellow onion medium, finely diced
- 4 garlic cloves minced
- 1 zucchini medium, diced
- 1 red bell pepper diced
- 8 oz cremini or baby bella mushrooms 225g, sliced
- 1 tsp dried Italian seasoning
- 1/2 tsp crushed red pepper flakes optional
- salt and black pepper to taste
- 24 oz marinara sauce 1 standard jar, about 680g
- 14.5 oz diced tomatoes 1 can, about 410g, drained
Ricotta Layer
- 15 oz whole milk ricotta cheese 425g; do not substitute part-skim
- 1 large egg
Cheese Topping
- 2 cups shredded low-moisture mozzarella cheese about 225g, divided into two 1-cup portions
- 1/2 cup Parmesan cheese about 50g, freshly grated, divided into two 1/4-cup portions
For Garnish
- 1/4 cup fresh basil leaves torn, for serving
Instructions
- Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish with olive oil or nonstick spray and set aside.
- Bring a large pot of salted water to a boil, then cook the spaghetti for 2 minutes less than the package directions. Drain (do not rinse) and set aside.
- Heat olive oil in a large skillet over medium heat. Cook the onion for 3 to 4 minutes until soft, then add the garlic and stir for 60 seconds. Add the zucchini, bell pepper, and mushrooms; cook for 6 to 7 minutes until tender and any liquid has evaporated. Season with Italian seasoning, red pepper flakes, salt, and pepper.
- Stir the marinara sauce and drained diced tomatoes into the skillet with the vegetables. Simmer over medium-low heat for 5 minutes, then remove from heat and taste for seasoning.
- In a medium bowl, stir together the ricotta, egg, 1/4 cup Parmesan, and a pinch of salt and pepper until smooth and well combined.
- Add the drained spaghetti to the skillet with the tomato vegetable sauce and toss thoroughly until every strand is coated and the vegetables are evenly distributed.
- Spread half the sauced pasta in the prepared baking dish, then layer with all of the ricotta mixture and 1 cup of mozzarella. Top with the remaining pasta, then scatter the remaining 1 cup of mozzarella and 1/4 cup of Parmesan evenly over the top.
- Cover the dish tightly with aluminum foil and bake at 375°F for 20 minutes.
- Remove the foil and bake for another 15 minutes, until the cheese is melted and golden. For a deeper golden top, broil for 2 to 3 minutes, watching closely.
- Let the casserole rest for 5 to 10 minutes before serving to help it set. Scatter torn fresh basil over the top and serve directly from the dish.
Notes
- Always undercook the pasta by 2 minutes before baking — it finishes cooking in the oven and this prevents a mushy texture.
- Use whole milk ricotta, not part-skim. Full-fat ricotta stays creamy after baking; part-skim can turn grainy and release extra moisture.
- Grate your own Parmesan from a block for best melt and flavor. Pre-grated contains anti-caking agents that prevent smooth melting.
- Make sure mushroom liquid fully evaporates before adding the sauce — this prevents a watery casserole.
- Make ahead: assemble the full casserole, cover tightly, and refrigerate up to 24 hours. Add 10 extra minutes to the covered bake time when going straight from fridge to oven.
- Storage: refrigerate leftovers in an airtight container for up to 4 days. Freeze (tightly wrapped) for up to 3 months; thaw overnight in the fridge before reheating.
- Reheat in a 350°F oven covered with foil for 15 to 20 minutes, or microwave individual portions with a splash of marinara on top to prevent drying out.
- Vegan swap: replace ricotta with cashew cream or seasoned firm tofu, use a flax egg (1 tbsp ground flaxseed + 3 tbsp water), and swap in vegan mozzarella shreds.
- Vegetable variations: spinach, eggplant, artichoke hearts, broccoli, or cherry tomatoes all work well — just cook down any high-moisture additions before adding the sauce.
- White sauce version: substitute the marinara with a creamy béchamel or alfredo sauce for a completely different but equally delicious bake.
Nutrition
Serving: 1ServingCalories: 490kcalCarbohydrates: 55gProtein: 26gFat: 18gSaturated Fat: 9gPolyunsaturated Fat: 1gMonounsaturated Fat: 6gCholesterol: 75mgSodium: 720mgPotassium: 620mgFiber: 5gSugar: 10gVitamin A: 22IUVitamin C: 45mgCalcium: 38mgIron: 19mg
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