3JJJ in Melbourne launched 22 October 1989, marking the first expansion of Triple J outside of Sydney (although some ABC regional local stations and ABC radio via AUSSAT were carrying Triple J overnight AFAIK)
6JJJ in Perth was next (29 October)… and Brisbane was the last in the metropolitan rollout of Triple J which also included Newcastle.
ABC FM initially began in Sydney, Melbourne, Adelaide and Canberra from 24 January 1976. As mentioned above it extended to Brisbane in 1980.
It had expanded to Newcastle, Ballarat, Rockhampton, Loxton, Mt Gambier, Perth, Bunbury, Hobart and Launceston by 1983. (Source: Dick Smith Catalogue, Data Section, 1983)
By financial year 1984-85 it had expanded to Darwin and about 20 further regional sites, bringing a total of 37 stations nationally. (ABC Annual Report, 1984-85) and 39 stations by 1986-87.