Cook the Pasta Boil the penne in salted water until al dente. Drain and set aside.
Sauté the Chicken In a large skillet, heat olive oil over medium heat. Add diced chicken breasts and cook until browned on all sides. Season with salt, pepper, and garlic. Cook until the chicken is no longer pink in the center.
Combine the Pasta and Sauce In the same skillet (or a large mixing bowl), combine the cooked penne, marinara sauce, and half of the mozzarella and Parmesan cheese. Stir well to coat everything evenly.
Transfer to Baking Dish Pour the pasta and chicken mixture into a greased 9x13-inch baking dish. Top with the remaining mozzarella and Parmesan cheese.
Bake to Perfection Preheat the oven to 375°F and bake for about 20 minutes, or until the cheese is bubbly and golden brown.
Garnish and Serve Remove from the oven and let cool for a few minutes before serving. Garnish with fresh basil or parsley for a burst of freshness.