Beaton also joined the National Amalgamated Union of Shop Assistants, and in 1911 was appointed as its full-time Scottish organiser, greatly increasing its membership in the nation. Through this position, he was active in the Scottish Trades Union Congress, serving as its treasurer in 1916/17 and its president in 1918/19. In 1919, he left the employment of the union to become an agent of the Scottish Co-operative Wholesale Society (SCWS), but initially he retained membership of the Shop Assistants' Union, and even served as its president in 1921/22.
