Preheat oven to 375°F; spray a 9x13-inch dish with cooking spray.
Cook penne according to package until just al dente; drain and return to pot.
Mix ricotta, egg, 1 cup mozzarella, Parmesan, Italian seasoning, and garlic powder in a large bowl.
Toss pasta with marinara to coat evenly.
Spread half the pasta in dish; arrange meatballs evenly over it.
Dollop ricotta mixture over meatballs; top with remaining pasta.
Cover tightly with foil; bake 25 minutes.
Uncover; top with remaining 1 cup mozzarella and bake 10 more minutes until melted and bubbly.
Let stand 5 minutes, garnish with fresh parsley, and serve hot.