He began his career at Spiked's predecessor, Living Marxism, the journal of the Revolutionary Communist Party, which ceased publication after ITN won their libel action against it.
Since then, O'Neill has contributed articles to publications in the United Kingdom, the United States and Australia including The Spectator, the New Statesman, The Guardian, BBC News Online, The Australian, The Christian Science Monitor, The American Conservative, Salon.com, and Rising East.