In a large bag with a zip top, add the vinegar, lemon juice, rosemary, garlic powder, and pepper.
Trim lamb chops of any visible fat and add to bag with seasoning. Turn to coat and refrigerate for 30 minutes.
Spray grill rack with nonstick cooking spray and place over medium hot grill. Remove chops from marinade, place on rack and grill, covered 6 minutes per side. Baste occasionally with remaining marinade.