In 10-inch skillet, cook sausage and onion over medium-high heat, stirring frequently, until sausage is no longer pink; drain. Stir in pepperoni, ketchup and pizza sauce.
Spray 1 1/2- to 3-quart slow cooker with cooking spray. Spoon sausage mixture into slow cooker. Stir in cheese.
Cover; cook on Low setting 2 to 3 hours.
Stir dip before serving. Serve with bread slices.