Preheat the oven to 375°F (190°C).
Cook the penne pasta according to package instructions until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat. Add diced onion and cook until softened, about 3-4 minutes.
Add minced garlic to the skillet and cook for 1 minute until fragrant.
Add ground turkey to the skillet. Cook, breaking it apart with a spoon, until browned and cooked through, about 6-8 minutes.
Stir in the marinara sauce, dried Italian seasoning, salt, and black pepper. Simmer for 5 minutes to combine flavors.
In a large mixing bowl, combine the cooked pasta and the turkey sauce mixture. Mix well.
Transfer half of the pasta mixture to a 9×13-inch baking dish. Sprinkle half of the mozzarella cheese and half of the Parmesan cheese over the pasta.
Add the remaining pasta mixture on top and sprinkle with the remaining mozzarella and Parmesan cheeses.
Bake uncovered for 20 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let cool for 5 minutes. Garnish with chopped fresh parsley before serving.