O'Reilly was an Irish Catholic priest, the oldest of the five children of Thomas and Mary O'Reilly of Cork, Ireland. He was educated at St. Colman's College, Fermoy and St. Patrick's College, Maynooth, studying philosophy and theology with the future Archbishop Mannix. O'Reilly joined the Vincentian order and was ordained in 1890. He came to Australia in 1892 as a preacher and then teacher; in 1903 was appointed President of St. Stanislaus College, Bathurst, a position he held until 1915.
O'Reilly became a leading advocate of the Catholic Federation's more aggressive espousal of the Catholic cause in public life (O'Farrell (1985): 300). He championed Catholic education rights; criticised the celebration of Empire Day rather than Australia Day and campaigned against conscription in World War I after initially supporting the war. He publicly defended Archbishop Mannix (q.v.) during the referendum campaigns, prompting a letter from Christopher Brennan (q.v.) to the Sydney Morning Herald on 30 November 1917 attacking O'Reilly, Mannix and the Sinn Fein. O'Reilly replied on 4 December that 'My erudite friend Mr. Chris Brennan is mistaken'. He argued Australia was experiencing an hysterical support for conscription akin to that over the relief of Mafeking during the Boer War (Clark (1980): 227). O'Reilly continued to fuel sectarian controversy in New South Wales over clerical access to influenza victims in 1918 and Ulster protestantism in 1922. (O'Farrell (1985): 340). The highlight of his political career was 'The Battle of Moore Park'. O'Reilly addressed a crowd of 150,000 gathered to protest the deportation of Father Jerger, a German Catholic priest. A contingent of diggers and their friends drove a wedge into the crowd and made a rush for the platform, attempting to lay hands on O'Reilly. The Catholic Press (3 June 1920) reported that 'With the glint of battle in his eye and a look of determination on his usually smiling countenance, he caught up a chair and holding it aloft with both hands, calmly invited the howling mob to "come on".' O'Reilly gave Workers Educational Association lectures and blessings at Trades Hall dinners. However, by 1927 he was disillusioned with the Irish cause as were many Australian clergy confronted by republicanism which they blamed for the Irish civil war.
In 1915 O'Reilly was appointed President of St. Vincent's College, Dublin, but a few months later he took up the position of Rector of St. John's College at the University of Sydney. He received his doctorate in sacred theology in 1920 and became Provincial of the Vincentian Order in Australia in 1925. He was also spiritual director of the St. Vincent de Paul Society 1923-1933 and represented New South Wales at the Irish Race Congress in Paris in 1922.
O'Reilly was a close friend of Christopher Brennan in his last years, inviting him to dinner at St. John's College once a week from 1928 when others were deserting him. He was appointed to the committee to administer the fund set up to assist Brennan and officiated at his funeral. It is also surmised that O'Reilly may have been a source for D. H. Lawrence's Kangaroo as they both shared a nine day voyage from Fremantle to Sydney on the Malwa in 1922 (Hall and Ruffels (1990):12-13). O'Reilly also wrote the lyrics and music to Australia : a national anthem (1920-1929?) which was initially published as a poem in Poems (1920). He left an uncompleted official biography of Cardinal Moran. At his funeral, the Bishop of Maitland, the Reverend Dr. Gleeson said: 'He was a lover of the classics, of art, of history and poetry, but he was a greater lover of the Catholic faith' (Sydney Morning Herald, 28.9.1933, p.15).
(Source: Adapted from Axel Clark Christopher Brennan : a critical biography (1980); Richard Hall and John K. Ruffels, 'Shipboard Talk: Did D. H. Lawrence Meet Fr. O'Reilly?' Overland 117 (1990): 11-14; Patrick O'Farrell The Catholic Church andCommunity : an Australian history (1985); 'O'Reilly, Maurice (1866-1933)' in ' Biographical Notes', The Turning Wave : poems and songs of Irish Australia, ed. Colleen Z. Burke and Vincent Woods (2001): 286-287; 'Rev. Dr. M. J. O'Reilly. Death of Noted Priest.' Sydney Morning Herald, 28.9.1933, p.15) and J. F. Wilkinson, 'Father Maurice O'Reilly: A Controversial Priest' Journal of the Australian Catholic HistoricalSociety 7 .3 (1983): 3-23).