A 1943 alumnus of the University of Chicago Booth School of Business, Reneker joined Swift & Company shortly after graduation. Prior to becoming president in 1964, he was responsible for industrial relations and coordination of the company's future planning. He became chief executive officer in 1967. On April 30, 1973, Esmark, Inc. was established with Reneker as president, and on October 20, 1973, he assumed the post of chairman and chief executive officer.
Reneker was a Trustee of the University of Chicago and a member of the Council on the Booth School of Business. He was president of the Community Fund of Chicago and the Economic Club of Chicago, and a president and member of the National Executive Board and the Boy Scouts of America. He has been identified also with a number of other business, civic, and educational organizations as director, trustee or board member.