The University Union was founded on the motion of John Monash to 'unite and bring into closer fellowship the members of the different schools to enable those who have entered upon their professional careers to keep up an active connection with the University, and to promote the common interests of members and the interests of the University'. The aim was undermined somewhat by the refusal of the Medical Students' Society (formed 1879) to participate. Set up in a poky room on the west side of the Quadrangle building, it published a magazine called the University Review and conducted smoke nights, socials and debates. Women students were granted separate rooms in the east wing to set up a similar body which they dubbed the Princess Ida Club . At much the same time students formed a range of more specialised groups, including the Science Club (1888), the Engineering Students' Society (1889), Historical Society, Musical Society, Philosophical Society, Law Society, University Militia and Christian Union.
The Union was not robust, overshadowed by the colleges and other societies until, following efforts by the newly formed SRC from 1907, it secured the use of the old National Museum as a Club House from 1910 when the Conservatorium of Music moved out.
A grant of £2000 from the Government and introduction of a compulsory levy from 1911 allowed for substantial remodelling.
The Union and the Princess Ida Club occupied the south end of the building and the north end was converted into a students' hall freeing up space in the North Extension to the Quadrangle. From this point it would be gradually transformed into a theatre . In the 1930s it was called the Common Room and Entertainment Hall. After World War I a wooden building purchased from the YMCA was purchased and placed behind the Old Museum to the west. It was converted into meeting rooms and a cafeteria.