He passed as a candidate for ministry and studied at Prince Alfred College in 1908, before spending two and a half years preaching from a motor launch on the Murray River between Swan Reach and Loxton.

He was publicly involved in the campaign against conscription during World War I, and unsuccessfully contested the 1918 state election in the electorate of Barossa, narrowly losing to Sir Richard Butler.

[6] In 1919, he was elected to the Australian House of Representatives as the Labor member for Angas, defeating long-serving Nationalist MP and Minister for Home and Territories Paddy Glynn.

[1] In the same year, the Sydney Morning Herald described Gabb as being an "unexciting speaker" and "a sort of inverted alchemist afflicted with an ambition for turning gold into lead.

"[10] He responded to criticism for wasting parliamentary time with quorum calls in May by stating "if the economy were really considered this show [parliament] would be shut down" and "close it and let me act as Mussolini and I will run things in a better way!

[13][14] He contested the 1938 state election as an independent, nominating against Premier Richard Layton Butler in his seat of Light, but was unsuccessful.