Stir together first 7 ingredients until blended.
Place lamb in a shallow dish or heavy-duty zip-top plastic bag; pour olive oil mixture over lamb. Cover or seal, and chill 8 hours, turning occasionally.
Soak wood chunks in water at least 30 minutes.
Prepare charcoal fire in smoker; let burn 15 to 20 minutes.
Drain wood chunks, and place on hot coals.
Remove lamb from marinade; pour marinade into water pan, and place pan in smoker. Add water to pan to depth of fill line.
Place lamb on lower food rack; cover with smoker lid.
Cook lamb 7 hours or until a meat thermometer inserted into thickest portion of lamb registers 150°. Add charcoal, wood chunks, and water to smoker as needed.