In a large covered skillet cook onions, sweet pepper strips, garlic, and dried basil (if using) in hot oil over medium heat for 8 to 10 minutes or until vegetables are tender, stirring occasionally.
Meanwhile, split loaves in half horizontally, slicing to, but not through, the other side. Hollow out loaves, leaving about 1/2-inch shell. (Reserve bread for another use.) Place opened loaves on a broiler pan. Arrange half the cheese in the bottom of loaves. Divide vegetables mixture over cheese. Top with remaining cheese. Broil 3 to 4 inches from heat for 1 to 2 minutes or until cheese is melted. Remove from oven. Sprinkle with fresh basil (if using). Fold bread tops over cheese. Makes 6 main-dish servings.