In A Large Skillet, Cook Beef And Onion Over Medium Heat Until Meat Is No Longer Pink; Drain. Stir In The Tomato Sauce, Salt And Oregano; Simmer For 5-10 Minutes. Cut Bread In Half Lengthwise And Then Widthwise. Spread Meat Mixture On Cut Side Of Bread; Sprinkle With Cheese, Olives And Pepperoni If Desired. Loosely Wrap Bread Individually In Pieces Of Heavy-Duty Foil (About 24 In. X 18 In.); Seal. Grill, Covered, Over Medium Heat For 15-20 Minutes Or Until Heated Through.