Preheat broiler, heat a charcoal grill until coals form white ash or preheat gas grill to medium.

To prepare sauce, in a small saucepan combine ketchup, vinegar horseradish, brown sugar, garlic and thyme. Mix well. Bring to a boil over medium-low heat. Cook, stirring frequently, until thickened, about 5 minutes. Remove from heat, stir in pepper.

Brush tops of chicken pieces lightly with sauce. Place chicken, sauce-side down, on a foil lined broiler pan or grill rack. Brush other sides lightly with sauce.

Broil or grill 3 inches from heat, basting with remaining sauce and turning until no longer pink in center, about 5-7 minutes per side. Let the chicken stand for 5 minutes before serving.