 Gross was also active in the international affairs activities of the ecumenical movement.He was a member of the Commission of the Churches on International Affairs of the World Council of Churches (CCIA/WCC) and he chaired the Department of International Affairs of the National Council of Churches of Christ in the USA (DIA/NCCCUSA) from 1954 to 1958.In that capacity he also chaired the NCCCUSA's Fifth World Order Study Conference on the Churches and World Order, in Cleveland, Ohio, 18–21 November 1958.