From the very conception of the Federal Government 1901 until 1956 all members of Parliment automatically became members of the Cabinet.

With the swearing in of the Robert Menzies Ministry on 11 Jan 1956 this was changed and a new system was introduced. This new system required some, but not all, members of the ministry would be members of the Cabinet. 

This practice was continued until the resignation of the McMahon Ministry on 05 Dec 1972.

When the Whitlam Ministry assumed office on 05 Dec 1972 the Government reverted back to the original practice which existed prior to 1956. All members of the ministry would be members of the Cabinet.

When the Fraser Ministry was sworn in on 22 Dec 1975, the structure of the cabinet was changed again. The system, which was introduced by the Menzies Government in 1956, was reintroduced. 

Once again Cabinet membership was by appointment only. This practice has been continued by all subsequent ministries.