1. Heat a charcoal grill until coals form white ash, or preheat a gas grill to medium. Place the grill rack 3 inches from the heat.
2. Combine the ketchup, vinegar, Worcestershire sauce, brown sugar and garlic in a small saucepan and mix well. Bring to a boil over medium-high heat. Cook, stirring continually, until thickened, about 3 minutes. Remove from the heat and stir in the pepper.
3. Brush the sauce on one side of each chicken piece. Arrange the chicken, sauce side down, on the grill rack and brush with sauce. Grill, turning and basting with the remaining sauce, until the juices run clear, 15 to 20 minutes.
Variations
For a delicious fruit flavor, add 2/3 cup apricot preserves or orange marmalade to the ketchup mixture before boiling.
For a spicier flavor, add 1/2 cup chili sauce to the ketchup mixture.
If you prefer an Asian twist, add 2 tablespoons soy sauce and 2 teaspoons grated fresh ginger to the marinade mixture.
Tip: Do Ahead
You can prepare the sauce up to 2 weeks in advance and keep it in the refrigerator. It will be ready to go when you are. But remember, the longer it sits, the stronger it gets.