Gather the ingredients.
Heat the oven to 350 F (180 C/Gas 4). Lightly grease or spray a 2 1/2 to 3-quart baking dish with nonstick cooking spray.
Heat the olive oil in a large skillet over medium heat. Add the ground beef, sausage, and onion. Cook, stirring until the meat is no longer pink and the onion is translucent.
Add the garlic to the meat mixture and cook, stirring, for 1 minute longer.
Add the crushed tomatoes, tomato paste, basil, oregano, and crushed red pepper. Cook, stirring occasionally, for about 10 to 12 minutes. Taste and add salt and pepper, as needed.
In a large bowl, combine the ricotta cheese, 1/2 cup of Parmesan cheese, the egg, and 1 cup of Mozzarella cheese. Stir until well blended.
While the sauce is simmering, cook the ziti in boiling salted water following directions on the package. Drain well.
Add the hot drained pasta to the bowl with the ricotta cheese mixture. Toss lightly to blend.
Add 2 cups of the meat sauce to the ziti mixture.
Transfer half of the pasta mixture into the prepared baking dish.
Spread about half of the meat sauce over the pasta, and then top with the remaining Parmesan cheese and half of the remaining Mozzarella.
Top with the remaining pasta mixture.
Then finish with the remaining meat sauce and remaining Mozzarella cheese and sprinkle with the chopped parsley.
Bake for 25 minutes, or until hot and bubbly around the edges.
Serve with garlic bread and a tossed green salad or Caesar salad.