Place chicken breasts in a resealable plastic bag set in a bowl. For marinade, in a small bowl combine wine or apple juice, oil, honey, mustard, garlic, pepper, and salt. Pour marinade over chicken; seal bag. Marinate in the refrigerator for at least 8 hours or up to 24 hours, turning bag occasionally.
Drain chicken, discarding marinade. Place chicken on the grill rack directly over medium heat; grill for 12 to 15 minutes or until done (170 degrees F), turning once halfway through grilling. Makes 8 servings.