1. Thaw lamb in refrigerator overnight if frozen. Remove fell (outer skin); trim any excess fat. Place leg, round side down, concave side on top.
2. Insert a small sharp knife along side exposed bone at top. With short strokes, cut along this bone, and cut meat down to the joint.
3. Begin again from top and release meat from other side of bone. With knife tip, follow the curve of the bone socket and release meat.
4. Make a slit along shin bone to free remaining meat from both sides, and then lift out bone. (Save the bone and any scraps for soup.)
5. Combine remaining ingredients in a large bowl; mix well. Add lamb, refrigerate overnight, turning often.
6. Grill lamb over hot coals 30 to 40 minutes, or until meat is cooked to desired doneness; turn several times and baste with remaining marinade during cooking.
