Peddie started his work in the co-operative movement for the Hull Co-operative Society as Publicity Manager and a director. He served in the Ministry of Information during World War II then became a director of the Co-operative Wholesale Society. He served on the boards of the Co-operative Insurance Society and the Co-operative Permanent Building Society (now the Nationwide). He was the President of Co-operative Congress in 1958.
Peddie also served on the national executive of the Co-operative Party and chaired the Party 1957-1965. He became a bridge between the co-operative and trade union movements, and the Labour Party, serving on the National Council of Labour, Co-op and Trade Unions. He served as President of both the Co-operative Congresses of 1958. Peddie was awarded an MBE, and was created Baron Peddie, of the City and County of Kingston upon Hull on 9 February 1961. He sat on the Labour benches as a Labour Co-operative peer.
He was one of the first members of the National Consumer Council and was appointed chair of the National Board for Prices and Incomes and of the Post Office Users Council. Peddie was also a governor of the British Film Institute and the Advertising Standards Authority.