Preheat oven to 450 degrees F or grill to medium-high. Spray one side of a 12 x 18-inch sheet of heavy duty aluminum foil with nonstick cooking spray.
Center one chicken breast on the sprayed side of foil. Spoon 1/4 of the pizza sauce over chicken. Top with 1/4 each of the pepperoni, vegetables and cheese.
Fold foil into packet. Repeat with remaining chicken breasts. Bake for 18 to 23 minutes on a cookie sheet in the oven or grill for 10 to 12 minutes, covered.
NOTE: Substitute or add your favorite pizza toppings.