Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
In a large skillet, brown ground beef and Italian sausage over medium heat. Drain off any excess grease.
Stir in marinara sauce and Italian seasoning. Simmer for 5 minutes.
In a separate bowl, combine ricotta cheese and Parmesan cheese.
Spread a thin layer of meat sauce in the prepared baking dish. Layer with half of the meat sauce, then dollops of ricotta mixture, and sprinkle with half of the mozzarella cheese. Repeat layers.
Bake for 30-35 minutes, or until bubbly and cheese is melted and lightly browned.
Let stand for 10 minutes before serving.
Notes
Serve hot with a side salad and garlic bread for a complete meal.