Heat oven to 375°F. Spray 8-inch square (2-quart) baking dish with nonstick cooking spray.
Cook ziti to desired doneness as directed on package. Drain.
In large bowl, combine cooked ziti, pizza sauce, pepperoni, bell pepper, Parmesan cheese, oregano and garlic; mix well. Spoon into sprayed baking dish; sprinkle with mozzarella cheese. Cover with foil.
Bake at 375°F. for 30 to 35 minutes or until mixture is thoroughly heated and cheese is melted.