Place steaks in single layer in resealable plastic food storage plastic bag or in 13x9-inch (3-quart) glass baking dish.
In small bowl, combine beer, brown sugar, pepper and Worcestershire sauce; stir until sugar is dissolved. Pour over steaks. Turn steaks to coat both sides. Seal bag or cover baking dish. Let stand at room temperature for 15 minutes to marinate.
Place steaks on broiler pan. Pour marinade into small saucepan; set aside. Broil steaks 2 to 4 inches from heat for 4 to 6 minutes. Turn steaks; top with onion rings. Broil an additional 3 to 5 minutes or until of desired doneness.
Meanwhile, bring marinade in saucepan to a boil. Reduce heat to low; simmer 2 to 3 minutes, stirring frequently. To serve, cut steak diagonally into thin slices; serve sauce over steak.