The WG class formed the original bogie open wagon fleet of the WAGR standard gauge lines. The wagons in this class were built in four groups at Midland Workshops between 1966 and 1973. The first batch (unlike later members of the class) had end doors. They were reclassified WGX in 1967. Ninety-three of the first batch were reclassified WGS in 1969-1970 and dedicated to superphosphate traffic although five were quickly returned to WGX in 1970. Two more were converted to WQX class flat wagons in 1969.
The second series wagons had no end doors. They were built in 1969 and 1970 at the same time as earlier wagons were being reclassified WGS for Superphosphate traffic. For a short period five wagons were coded WGN for use on Nickel concentrate traffic but these had all returned to WGX by 1977 (including 5 that had been class WGS). The final 25 wagons WGX 33209-33233 were built in 1973.Between 1979 and 1981 the WGX class were recoded WOAX under the 1979 ROA system. The WGS were included in this too and so returned to the fold as WOAX. However, another small fleet was created for wagons dedicated to Gypsum traffic which became class WGG. Later there was a steel carrying conversion WOSF. Some of the WOAX became WOAS during the 1080s for a short period.
From 1988 disposal started. Some wagons were reclassified for Nitrate traffic and labelled for "Dangerous Goods" as class WODX. There was also a steel carrying conversion (WOSF) and a single wagon converted to class WOO. A small number of WOSF became WOSX.
In January 1980 nine wagons from three classes were reclassified WGG for Gypsum traffic. Further reclassifications followed, both to and from class WGG.
WGL 631 was built for Western Mining Co. in December 1976 to carry Nickel Matte. It was followed by 2 more new wagons in 1977. Further additions to the class were by conversion from class WFN. There were four conversions in 1979 and a further five in 1984. The similar WAGR owned wagons in class WGLA were converted from WFDY and WSA in 1985.