In 1908, the WMR and its locomotive fleet was purchased by the New Zealand Railways Department (NZR) and incorporated into the national rail network, and although No. 16 bore a likeness to members of the O class, it was sufficiently different that it warranted separate classification. Technical differences were sufficient that it was not classified with the visually similar WMR No. 13/NZR OA 457, and it became OC 458. It is known to have operated on the line from the Hutt Valley through the Rimutaka Range to the western end of the Rimutaka Incline, and its final depot was at Cross Creek at the eastern end of the Rimutaka Incline in the Wairarapa. It was withdrawn from service in July 1930.