In 1899, the QR introduced a new type of passenger locomotives designed by Henry Horniblow and L.W. Piggott. It had much in common with the B15, but larger drivers with a diameter of four instead of three feet. The firebox had the same size, but the boiler barrel was a bit longer. Although the total weight on drivers had been increased by 5,500 pounds, the load on the heaviest axle was still limited to eight tons. The designation was PB15, where P stood for “Passenger”, B for three driving axles and 15 for the cylinder diameter in inches.

Between 1899 and 1912, a total of 202 locomotives had been built by several manufacturers. In 1924 the North Ipswich Workshops built another one for the Aramac Shire Tramway, but this locomotive was instead placed into service by the QR. In 1925 and 1926, Walkers built 30 more for the QR which had Walschaerts instead of Stephenson valve gear and larger tenders. In 1932, seven received a second sandbox for reversing to use them for shunting on colliery branches. Five were preserved of which one is still operational at the Queensland Pioneer Steam Railway.