Creating the Best Veggie Pasta Bake can be straightforward if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish.
2. Cook Pasta: In a large pot, cook the penne pasta according to the package instructions until al dente. Drain and set aside.
3. Sauté Vegetables: In a large skillet, heat olive oil over medium heat. Add onion and garlic, sautéing until softened.
4. Add Bell Pepper: Stir in the bell pepper, zucchini, and yellow squash. Cook for about 5-7 minutes until veggies begin to soften.
5. Incorporate Spinach: Add the spinach and cook until wilted. Then stir in the drained tomatoes.
6. Season: Sprinkle in Italian seasoning, salt, and black pepper, mixing everything well.
7. Combine Mixtures: In a large bowl, combine the sautéed vegetable mixture with the cooked pasta and marinara sauce. Mix until evenly coated.
8. Layer Cheese: Spread half of the pasta mixture into the prepared baking dish. Sprinkle with half of the mozzarella and Parmesan cheeses. Layer the remaining pasta on top, finishing with the rest of the cheese.
9. Bake: Cover the dish with foil and bake for 25 minutes. Remove foil and continue baking for an additional 10-15 minutes, or until the cheese is bubbly and golden.
10. Rest: Once baked, allow the pasta bake to rest for 10-15 minutes before serving to let it set up.

These steps will help you create this incredible veggie pasta bake with ease!