In 1946, he was appointed director of the Office of Economic Stabilization and became chairman of the Economic Stabilization Board for President Harry S. Truman. Bowles ran unsuccessfully for the Democratic gubernatorial nomination in Connecticut that year. Also in 1946, he became one of the American delegates to the first conference of United Nations Economic, Scientific and Cultural Organization UNESCO in Paris. Bowles served as special assistant to UN Secretary General Trygve Lie in 1947 and 1948. During these years, the UN General Assembly met in session at Lake Success, New York on Long Island, as the UN building in Manhattan was not completed until 1952 He continued with the United Nations as international chairman of the United Nations Children's Appeal from 1948 to 1951.