How to Make It
Combine rosemary, oil, 1/4 teaspoon salt, and garlic; rub mixture evenly over both sides of lamb. Cover and marinate in refrigerator for at least 2 hours or overnight.
Sprinkle both sides of lamb with remaining 1/4 teaspoon salt and pepper. Place lamb on a grill rack coated with cooking spray; grill 3 minutes on each side (145° for medium-rare) or until desired degree of doneness.