Brown meat; drain. Add onion and green pepper; Cook until tender. Add barbecue sauce, mushrooms, and salt; simmer 15 minutes. Cut lengthwise slice from top of bread. Scoop out center, leaving 1 inch shell. Place half of cheese in shell; fill with hot meat mixture. Cover with remaining cheese and top bread slice. Wrap in foil. Bake at 400 degrees for 10 to 12 minutes.