Preheat grill for direct-heat cooking. Or position broiler rack so that top of meat on rack in pan will be 4 inches from heat source; preheat broiler. In pot, mix beer with barbecue and Worcestershire sauces; over medium-high heat, bring mixture to boil. Cook, stirring occasionally, until thickened, 5-7 minutes. Remove from heat; cool.
Rub all sides of steaks with seasoning. Place on grill or rack set in broiler pan. Grill or broil, turning once, 3-4 minutes per side for medium-rare, brushing with half of sauce after turning. Transfer to platter, sauce side down; brush with remaining sauce. If desired, sprinkle with parsley.