He was working as a relief teacher in Queensland when he first came into contact with the Catholic Worker Movement (CW), founded in the United States by Dorothy Day and Peter Maurin during the Great Depression. O'Reilly subsequently founded Brisbane's West End Catholic Worker community along with Jim Dowling and Angela Jones, aiming to address social issues including youth homelessness among the Aboriginal community. He described the CW as composed of three practices which together constitute a life of integrity: living in intentional community, practicing the works of mercy, and nonviolent prophetic witness. He aims to personally enact this through living in community with the poor, prison visitation, and direct action against war. Catholic Workers in Brisbane were also concerned about the threat posed by nuclear weapons and the uranium mining industry and its direct and indirect effects on those in the Third World. Together with other members of the Brisbane Catholic Worker, he took an active role in highlighting the involvement and complicity of the Australian government, corporate and military sectors in supporting Indonesia's brutal and illegal 25-year occupation of East Timor.