In a bowl, combine ketchup, molasses and steak sauce. Place 1/2 of the mix in a plastic resealable bag. Add 1/3 cup dressing and garlic to mix in bag. Add steak to marinade. refrigerate 2 hrs, turning once.
Add remaining dressing to ketchup mix, reserve. Oil grill grates and heat for direct cooking over medium. Remove steak from marinade. Sprinkle steak w/ salt and pepper.
Place steak on grill. Cook 5 mins. Turn over and grill another 5 mins, brushing w/ reserved sauce. Let stand for 10 mins before slicing.