Preheat your oven to 375°F (190°C).
Cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, add a drizzle of olive oil over medium heat. Sauté the diced onion until translucent, about 5 minutes. Add the minced garlic and cook for another minute.
Add the Italian sausage to the skillet. Use a spatula to break it apart as it cooks until browned and fully cooked, about 7-10 minutes.
Stir in the crushed tomatoes, dried oregano, salt, and pepper. Let the sauce simmer for about 5 minutes to meld the flavors together.
Combine the cooked penne pasta with the sausage and sauce mixture, stirring to coat the pasta evenly.
Transfer the pasta mixture into a large baking dish. Sprinkle the top with shredded mozzarella and grated parmesan cheese, evenly distributing it.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes. Garnish with fresh basil before serving.