There had been an Allan Glen Association that had held periodic meetings attended by former pupils and members of school staff from 1894 to 1922, but it was not until 1923 that the Old Boys’ Club was formally constituted.

At the time of the school centenary in 1953 it was noted that it had over 1500 members and sponsored, at various times, angling, bridge, badminton, cricket, curling, golf, rugby, sailing, and a male voice choir. In addition to the parent club there were branches in London, the Midlands of England and Edinburgh. There were also for brief periods sections in Lincoln, North West England and Ontario, Canada.

Over the years the club maintained excellent relations with the school and made a number of presentations to the school. The club also helped in obtaining the playing fields at Bishopbriggs and the building of the pavilion.

In its early years the main activity of the club was the organisation of the annual dinner but its activities soon expanded to cover a wide range of social and other activities that included for a number of years a very successful dinner-dance, and a luncheon club, which like the annual dinner is still in existence. The Club was also instrumental in setting up the Allan Glen's Endowment Scholarship Trust, and the Trustees include certain office bearers and members of the Club. The club is also examining further ways of keeping Allan Glen's name involved with education and particlarly science and engineering education.