The first general meeting of the Australian Bar Association was held in Hobart on 24 January 1963 during the Thirteenth Legal Convention of the Law Council of Australia. The first draft of the constitution of the ABA was prepared by Nigel Bowen QC (as he then was) and settled by representatives from the Victorian, New South Wales and Queensland Bars.
In welcoming the formation of the ABA, the then Attorney-General for the Commonwealth, Garfield Barwick QC (as he then was) said that “Its task is to maintain the proud tradition of independence, courage and skill which have characterised the Bar in its best days, and without which no community can properly secure the continuance of the Rule of Law.”
Some documents concerning the establishment of the ABA are set out in the links below, including its first Constitution.
Hart, G; Helman, John --- "The Founding of the Australian Bar Association"  AUBarGaz 2; (1968) 2(3) Aust Bar Gaz 3
The first few pages of The Australian Bar Gazette Volume 1, Number 1