O'Leary received her bachelor's degree from Fisk before earning her Bachelor of Laws degree from Rutgers School of Law. O'Leary worked as a prosecutor in New Jersey and then in a private consulting/accounting firm before joining the Carter Administration. O'Leary returned to the private sector and rejoined the government as the first Secretary of Energy of the Clinton administration. As Secretary of Energy, O'Leary declassified documents detailing how the United States had previously conducted secret testing on the effects of radiation on unsuspecting American citizens. O'Leary received criticism for her excessive spending as Secretary.