In medium skillet, cook ground beef and onion until beef is brown and onion is tender. Stir in tomato sauce, salt and oregano. Place each loaf half, crust side down, on pieces of foil large enough to wrap up sandwich. Spread 1/2 meat mixture on each loaf. Sprinkle each loaf with cheese and olives. Wrap up foil, folding to seal. Heat over low coals 15 minutes, or until heated through. Or heat in 350 degree oven for 25-30 minutes.