In a bowl, mix together ground beef, Montreal Steak Seasoning, ketchup, bacon and dill weed. Shape into four patties. Brush onion slices with oil. Place patties and onion slices on grill over medium heat. Grill for 8 to 12 minutes or until burgers are well done (160�F internal temperature) and onion is tender, turning once. Add cheese slices to each burger one minute before cooking is completed. Place on hamburger rolls. Top with lettuce and tomato.