Born George Oliver Onions on 13 November 1873 in Bradford, Yorkshire, England, UK, of humble parents. He studied art for three years in London at the National Arts Training Schools (now the Royal College of Art). In the book Twentieth Century Authors, Onions described his interests as motoring and science; he was also an amateur boxer as a young man.
In 1909, he married the writer Berta Ruck (1878–1978), and they had two sons, Arthur (b. 1912) and William (b. 1913). In 1918, legally changed his name to George Oliver, but continued to publish under the name Oliver Onions.
He died on 9 April 1961 in Aberystwyth, Wales.