O'Reilly went to North Sydney Boys High School,[1] leaving at 14 years of age.
Returning to Sydney after a trip to Europe, he studied for the Leaving Certificate at night school.
[2] At 14, O'Reilly started training as carpenter and at 16 travelled to England as companion and carer to a man with a disability.
[2][3] After his ordination he was the minister at a number of Methodist churches throughout New South Wales, later taking positions with the Methodist Conference and Methodist schools and higher education (including Vice Principal of Leigh College, 1949–1959; Principal of Methodist Ladies' College, Burwood, 1960–1965;[3] Connexional Secretary, 1964–1974; Secretary of Conference, 1968; President of Conference, 1969; Secretary General, 1972–1974; President-General, 1975–1977.
[3] He was founding member of the NSW Council of Social Service and one of the founders of the Australian Council of Social Service (ACOSS, he later became ACOSS's chairman).