Wash chicken thoroughly. Pat dry. Rub both sides with half a lemon. In a small bowl mix garlic and spices. Rub mixture on both sides of chicken. Place the chicken halves, skin-side up, in a shallow baking dish. Allow the chicken to stand covered in refrigerator for 24 hours.
Place the chicken halves, skin-side up, 4-5 inches from mesquite coals. Cover and grill for 20 minutes, turn and grill at 20 to 30 minutes intervals. Total cooking time is about 1 1/2 hours.