Preheat the oven to 190°C (375°F).
In a large oven-safe pot or Dutch oven, heat the olive oil over medium heat.
Add the chopped onion and sauté for 3-4 minutes until translucent.
Add the minced garlic and cook for another 1 minute until fragrant.
Add the diced red bell pepper, zucchini, and sliced mushrooms to the pot and cook for 5 minutes, stirring occasionally.
Stir in the dried penne pasta, canned diced tomatoes (with their juice), vegetable broth, dried oregano, dried basil, salt, and black pepper.
Bring the mixture to a boil, then cover the pot with a lid and transfer it to the preheated oven.
Bake for 25 minutes, stirring halfway through to prevent sticking.
Remove the pot from the oven and stir the pasta mixture.
Sprinkle the shredded mozzarella and grated Parmesan cheese evenly over the top.
Return the pot to the oven, uncovered, and bake for an additional 10 minutes until the cheese is melted and bubbly.
Remove from the oven and let it cool for 5 minutes.
Garnish with fresh basil leaves before serving.