In a large combine the first three ingredients (through pepperoni); mix well. Shape mixture into four 3/4-inch-thick patties.
Grill burgers, covered, over medium heat 14 to 18 minutes or until done (160 degrees F), turning once. Toast bread slices on the grill. Meanwhile, in a small saucepan heat pizza sauce over low heat. Serve burgers between toasted bread slices topped with sauce, cheese, and, if desired, additional pepperoni slices.