He was invited to interview for the general counsel position at the United States Department of Health, Education and Welfare, but again declined because he felt the agency was too big and it was outside his specialty. His political activities led William J. Casey, chairman of the Securities and Exchange Commission (SEC), to interview him for the general counsel job there in summer 1971. Cook was appointed to the position on September 1, and sworn in on September 7. In 1972, Chairman Casey reorganized the SEC to create Market Regulation, a regulatory division. Cook was appointed associate director of the new division, and retained his job as general counsel. Cook's opportunity to vault to the chairmanship of the SEC came just a year later.