First, preheat your oven to 200°C (390°F).
Cook the Penne pasta until it’s al dente, following the package instructions. Drain the pasta and set it aside.
While the pasta is cooking, heat olive oil in a large pan over medium heat. Sauté the garlic and onions until they release a pleasant aroma and the onions become translucent.
Incorporate the zucchini and bell peppers into the pan, and season them with salt and pepper. Sauté the vegetables until they reach a slight tenderness.
In a large mixing bowl, combine the cooked pasta, sautéed vegetables, and marinara sauce. Mix thoroughly to ensure everything is evenly coated with the sauce.
Transfer the pasta and vegetable mixture into a baking dish and sprinkle shredded mozzarella cheese on top.
Place the dish in the preheated oven and bake for 20-25 minutes or until the cheese is melted and slightly golden.
Allow the pasta bake to cool for a few minutes before serving. For a final touch, garnish with fresh basil leaves.