In a large screw top jar, combine wine, oil, soy sauce, Worcestershire sauce, mustard and pepper to taste. Cover and shake until blended. Arrange chicken in a large plastic bag set in a shallow pan. Pour marinade over chicken, forcing as much marinade up and around chicken as possible. Tie bag tightly closed. Refrigerate chicken 4 to 6 hours, turning bag over once. Grill or broil chicken, turning often, until juices run clear.