In a small bowl stir together the garlic, rosemary, olive oil, salt and pepper. Place the lamb chops in a shallow dish and pour the marinade over them, turn the chops to coat both sides. Cover and refrigerate at least 2 hours.
Start a fire in a charcoal grill or preheat a gas grill. Place the chops on the rack over high heat and grill turning once, 5 minutes per side for medium rare. The outside will be well seared with the insides still pink.