Which parameters affect coalition building in budgetary negotiations? In this article, three distinct levels of analysis are identified to account for coalition building patterns, associated with domestic politics, domestic socioeconomic structures and EU politics. At the level of domestic politics, ideology points to cross-governmental affinity of a partisan nature; at the level of socioeconomic structures, similarity of policy interests, generated by cross-national socioeconomic convergence with EU policy standards, informs coalition formation patterns; at the EU politics level, the intergovernmental power balance influences the political aspirations of each Member State in the integration process and coalition-building decisions. Two sets of parameters affect the evolution of EU coalition patterns, corresponding to the integration impact on the EU (new cleavages) and on the Member States (the impact of Europeanisation). This analytical framework is used to examine the southern coalition (Spain, Greece, Portugal) in the four multi-annual financial frameworks (1988, 1992, 1999 and 2005).