In a small saucepan mix ketchup, vinegar, brown sugar, horseradish, Worcestershire sauce, OLD BAY, mustard and garlic powder. Simmer over low heat 10 minutes then remove from heat. Set aside.
Lightly brush chicken pieces with oil. Sprinkle generously with OLD BAY. (Mmm.)
Grill chicken over medium heat with lid closed about 40 minutes or until chicken is cooked through, turning occasionally. Brush chicken with Barbecue Sauce during last 10 minutes of grilling. Serve with additional Barbecue Sauce on the side.
Test Kitchen Tip: Prepare as directed, using 2 1/2 pounds boneless skinless chicken breasts or thighs. Grill chicken over medium heat 6 to 8 minutes per side or until cooked through, brushing with Barbecue Sauce during cooking. Serve on rolls with lettuce, tomato and red onion for an easy, flavorful grilled chicken sandwich.