Preheat the oven to 375°F (190°C).
Cook the ziti in salted boiling water until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat.
Cook the onion until softened, then add the garlic and cook for 30 seconds.
Add the ground beef and Italian sausage. Cook until browned and drain excess grease.
Stir in the marinara sauce, Italian seasoning, salt, and black pepper. Simmer for 15 to 20 minutes.
In a large bowl, combine the ricotta cheese, egg, half of the Parmesan cheese, and chopped parsley.
Mix the cooked pasta with the meat sauce until evenly coated.
Lightly grease a 9x13-inch baking dish.
Spread a thin layer of sauce on the bottom.
Add half of the pasta mixture.
Top with half of the ricotta mixture in small spoonfuls.
Sprinkle with half of the mozzarella cheese.
Repeat the layers with the remaining pasta, ricotta mixture, mozzarella, and Parmesan.
Cover with aluminum foil and bake for 25 minutes.
Remove the foil and continue baking for 15 to 20 minutes until the cheese is melted and bubbly.
Broil for 2 to 3 minutes until lightly golden if desired.
Let the baked ziti rest for 10 to 15 minutes before serving.
Garnish with fresh basil and extra Parmesan cheese.