In 1966, just out of high school, she entered the novitiate of the Sisters of the Humility of Mary, of Villa Maria, Pennsylvania, in order to "have an impact on the world".

In this role she negotiated for gay and lesbian rights to be included on the discussion in a conference marking the year in Houston, Texas.

Other speakers included Rosalynn Carter, Betty Ford, Lady Bird Johnson, Bella Abzug, Barbara Jordan, Audrey Colom, Claire Randall, Gerridee Wheeler, Cecilia Burciaga, Gloria Steinem, Lenore Hershey.

It was one of the first to respond to the HIV/AIDS epidemic's implications for legal and civil liberties, using aggressive litigation to ensure AIDS patients' access to treatment.

"[13] O'Leary was referring to the Lavender Menace, a description by second wave feminist Betty Friedan for attempts by members of the National Organization for Women (NOW) to distance themselves from the perception of NOW as a haven for lesbians.

They staged a protest in 1970 at the Second Congress to Unite Women, and earned the support of many NOW members, finally gaining full acceptance in 1971.

[15] O'Leary, and her advocacy for the inclusion of lesbian and gay rights in the 1977 National Women's Conference, is portrayed by Canadian actress Anna Douglas in the FX television miniseries Mrs America.