in 1901 o'reilly helped to found the guild of st. elizabeth, a settlement house in south boston. she was active in the women's educational and industrial union, the boston public library, the tuberculosis society, and the massachusetts conference of charities. o'reilly was appointed to the state prison commission in massachusetts in 1907, to oversee children's institutions, including reformatories and orphanages. she resigned that position in 1911. reform writings by o'reilly included a 1910 exposé on "baby farms" in new hampshire, and another in 1913, on unsafe working conditions in canneries. "the canned food consumed by the people of the united states is prepared, only too often, amid conditions of revolting filth, by workers whose bodies are unclean and diseased, and who are forced to live and work in an environment that makes cleanliness and health impossible," she wrote, after going undercover as a cannery worker. she testified before a congressional committee about the conditions she saw among women in the canneries.