Preheat grill for direct heat cooking. Or position broiler rack so that top of meat on rack in pan will be 4" 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 steak 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 half of sauce after turning. Transfer to platter sauce side down; brush with remaining sauce. If desired, sprinkle with parsley.