Drawing on extensive multi-archival and multi-institutional research, the article explores how the Committee of Professional Agricultural Organisations (COPA) responded to the multiple challenges presented by the Memorandum ‘Agriculture’ between 1968 and 1972. At this critical juncture, COPA had to show its ability to unite and mobilise Community farmers against the Commission’s first major reform of the Common Agricultural Policy. The article demonstrates that the transnationalisation of farm protests, which culminated in the March 1971 demonstration, was the result of COPA’s attempt to avert marginalisation and address internal contestation by its member organisations. The article also sheds light on the internal, structural, and ideological factors behind the gradual deterioration of the close COPA-Commission alliance, which forced COPA to supplement its traditional insider lobbying strategy with transnational grassroots mobilisation leading up to the March 1971 protests.