How to Make It
Combine all Marinade ingredients in a 1-gallon ziplock plastic freezer bag. Set aside 1/4 cup of the marinade. Add lamb to marinade in bag. Gently massage bag until lamb is well coated in marinade. Seal bag, squeezing out excess air. Lay bag flat on a small rimmed baking sheet, and place in refrigerator. Chill 3 hours, turning bag once or twice.
Remove from refrigerator, and let stand 40 minutes.
Preheat grill to medium-high (400°F to 450°F). Remove lamb from marinade; reserve marinade. Season chicken with salt and pepper to taste, if desired. Grill lamb, uncovered, on lightly oiled grill grates until a meat thermometer inserted in thickest portion registers 135°F, about 8 minutes per side, basting occasionally with reserved marinade from bag.
Let lamb stand 10 minutes. Slice and serve with reserved 1/4 cup marinade.