He became a school inspector and subsequently Secretary of the Department of Education in the newly formed Irish Free State.
He wrote five novels, of which the best-known was Land Under England (1935), a science-fiction account of a totalitarian society ruled by telepathic mind control.
The novel combines elements of a "lost race" narrative (the descendants of a Roman legion live underground under the north of England) with fears of totalitarian control.
Wind from the North was later a standard Irish primary school text in the 1950s, in an edition published by Browne & Nolan.
Giffuni, C. "Joseph O'Neill, a Bibliography," The Journal of Irish Literature, Volume XVI Number 2 May 1987.