As a coach of national teams, Penn was undefeated. He also served as an assistant to All Blacks coach Alex Wyllie and was a member of the selection panel which chose John Hart as All Blacks coach.
Penn's coaching career included leading national teams to victory without any losses. He also worked as an assistant for All Blacks coach Alex Wyllie and was a member of the panel that selected John Hart as the new All Blacks head coach.