October 15, 1952, at a regular Mattachine Guild meeting, a few members brought forth the concept of an organizational voice. This idea was outside of the agenda and members interested in further discussion were asked to adjourn to the kitchen. That evening the concept of a homosexual magazine was conceived and over the next two months a new organization, ONE, Incorporated was formed. In January 1953, the first issues were sold for 25 cents each, the same price as a beer at the time. By April 1953, the magazine offered the opportunity of full-time employment for Legg as Business Manager and an occasional weekly pay check of $25.00. He wrote articles under a number of pseudonyms including; Holister Barnes, Richard Conger, Marvin Cutler, W.G. Hamilton, William Lambert, Wendy Lane, Valentine Richardson, and Sidney Rothman.
Legg believed that education could be transformative in gaining society's acceptance of gays and lesbians. In 1956, he championed the establishment of The Institute of Homophile Studies, the first institute in the United States dedicated to the study of homosexuality. The Institute proved a range of educational opportunities and received state accreditation for a period during the 1980s. Using his pseudonym, Marvin Cutler, as editor, ONE, Inc. published, Homosexuals Today: A Handbook of Organizations and Publications. Legg and the editor of ONE Magazine, Don Slater, struggled over the future direction of the organization in 1965. Legg's faction won the right to continue using the name "ONE" in 1967. During this time, Legg contributed to the founding of the Southern California Council of Religion and the Homophile (SCCRH) in 1966, an organization formed to improve relations with mainstream religions and address the spiritual needs of the gay and lesbian community. In 1976, Vern L. Bullough, Barrett W. Elcano, W. Dorr Legg, and James Kepner published their edited work the Annotated Bibliography of Homosexuality, a survey of gay and lesbian literature. The following year, Legg contributed to the founding of the "Lincoln Republicans," which became the Log Cabin Club. A ballot initiative to ban public school employment of gays, lesbians, and possibly anyone that supported gay rights had spurred the formation of the organization. Legg's final collaboration in publishing was a history of ONE Institute and its educational efforts with David G. Cameron and Walter L. Williams, Homophile Studies in Theory and Practice. In 1960 Legg and John Nojima had started dating and they remained together until Legg's death in 1994. Nojima played a key role in supporting Legg financially and recording many ONE events. Legg died in their home in his sleep on July 26, 1994.