[1] O'Kane joined the Northern Ireland Labour Party (NILP) in Newtownabbey, and was briefly also active in People's Democracy.
By the early 1970s, he was prominent in the "Workers' Association for the Democratic Settlement of the National Conflict in Ireland", a group linked to the British and Irish Communist Organisation, which was influential in the Newtownabbey NILP.
[2] In 1972, he was one of nine Workers' Association members who chained themselves to radiators at the Department of External Affairs in Dublin, calling for the Irish government to recognise Northern Ireland.
He gradually rose to prominence, being elected as secretary of the Belfast branch in 1974, then to the National Executive in 1979, as chair of the salaries committee in 1982, and president of the union in 1987.
In 2002, he succeeded de Gruchy as General Secretary, and immediately negotiated a merger with the NUT and Association of Teachers and Lecturers.