George McCullagh Reed was born in County Monaghan, Ireland, probably in 1831 or 1832, the son of James Reed, a farmer, and his wife, Jane Ann Lewis. Little is known of his early life. He graduated from Queen's College, Belfast, in 1856, and after being ordained as a Presbyterian minister spent some time in France and Switzerland. In 1857 he emigrated to Victoria, Australia, where he took charge of the North Melbourne Presbyterian Church. He later became the first moderator of the United Presbyterian Church of Victoria.
In 1861 Reed became minister of the Presbyterian church in Ipswich, Queensland. On 6 July 1863 at Ipswich he married Jessie Chalmers Ranken. He resigned his ministry in 1866 and successfully contested the parliamentary seat of Ipswich which he held until May 1867.
The remainder of Reed's career was spent principally in newspapers in New Zealand, Australia and Britain. In 1869 or 1870 he moved to Auckland, New Zealand, where, with William Tyrone Ferrar, he set up the Evening Star. Henry Brett joined as an equal partner in March 1870.
Reed had a brief spell as a politician in Auckland, representing Takapuna in the Auckland Provincial Council from 1873 to 1876, and serving as provincial treasurer from 1873 until his resignation in November 1874. That year he was one of three prominent Aucklanders who induced Sir George Grey to enter provincial and then colonial politics.
In 1876 Henry Brett apparently struck a deal with George Jones to wind up Jones's newspaper, the Echo, which had been the main rival to the Evening Star. Reed moved to Dunedin and, possibly with financial assistance from Brett, established a new paper, the Evening News, to support the threatened provincial system. In April 1876 Reed and George Fenwick purchased a Dunedin morning paper, the Otago Guardian. Later that year they became partners in the Evening News. Dunedin was unable to support two morning dailies, and in October 1877 Reed and Fenwick acquired their rival, the Otago Daily Times and its weekly edition the Otago Witness; Reed edited both papers. The partners then closed the Guardian and its weekly, the Southern Mercury.
In the early 1880s Reed spent some time in Melbourne as leader writer on the Argus, then, in 1883, joined the New Zealand Herald, contributing a column, 'Calamo currente'. He moved to Britain to become the Herald's correspondent and started the short-lived Australian Times and Anglo-New-Zealander. In 1886 he was back in New Zealand as editor of the Auckland Evening Bell, in furious competition with his old partners at the Star. He also revived his New Zealand Herald column.
The Evening Bell collapsed in May 1888 and Reed joined the Herald full time. In 1889, once again in Australia, he became editor of Melbourne's short-lived Evening Standard; in 1890 he was leader writer to the Sydney Morning Herald; and in 1895, his final move, he rejoined the New Zealand Herald as a leader writer and a popular columnist under the pen-name 'Colonus'.
Reed's journalistic style was 'virile and forceful, its effect heightened by a habit of mind which was enthusiastic rather than judicial'. He was of an 'ardent and impulsive nature', 'full of reforming zeal' and a strong advocate of liberal opinions who could trenchantly champion the oppressed and castigate hypocrisy. When disquiet was expressed at the pardon given to Te Kooti in 1883, Reed claimed that Te Kooti had 'only paralleled barbarities which make up a great part of British history'. An outburst by Judge T. B. Gillies during a celebrated rape trial was put down to 'undigested lobster and disordered spleen'. Nor was Reed above a practical joke. In 1883 for April Fool's Day he reported that Noah's Ark had been discovered intact in a glacier on Mt Ararat; the story was reprinted by papers throughout the world.
Reed published two books: Calamo currente (1887), a collection of his columns, and The angel Isafrel: a story of prohibition in New Zealand (1896), a novel. He was a member of the Auckland Hospital and Charitable Aid Board, a promoter of the Auckland Anglo-Israel Association and an active Freemason. He died of a heart attack in Auckland on 13 November 1898. He was survived by three sons and two daughters; the date of Jessie Reed's death is not known.