Preheat the oven to 350°F. Spray a 3-quart baking dish with nonstick spray.
Cook the ziti as directed on the package, using the minimum cook time. Then drain, and return the pasta to the pan.
Meanwhile, in a 12-inch skillet, cook and stir the sausage, onion, bell pepper and garlic over medium-high heat for about 7 minutes (or until the sausage is no longer pink and the onion is soft). Stir in the pizza sauce, bacon and pepperoni.
Pour the sausage mixture over the cooked pasta; stir. Spoon half of the pasta mixture into the prepared baking dish. Sprinkle with 1 cup of the cheese. Spoon the remaining pasta on top.
Bake, uncovered, for 30 minutes. Top with the remaining 1 cup of cheese. Bake 5 to 10 minutes longer or until hot in the center and the cheese is melted and bubbly.