Previous analysis has looked at the interface between organized civil society (OCS) and European Union (EU) institutions and has posed questions about their role as political communicators for the EU project, and consequently their independence, representativeness, and policy influence. While these accounts focus in part on the role of European OCS in helping the EU institutions in the process of identity building, this work differs in offering an account of the internal processes that build identification and community within EU OCS coalitions. These dynamics are examined using social movement theory on coalitions and communities applied to a diverse coalition of OCS working on a range of social change issues at EU level known as the Platform of European Social NGOs (the Platform). Aside from a broad ideological alignment based on support for a stronger social policy at EU level, the composition of the Platform remains diverse. While diverse organizations can cooperate effectively in loose episodic and strategic alliances, the continuity in and density of collaboration within this coalition are notable. In the process of coalition work Platform members are influenced by external frames that circulate at EU level; they are also involved in a process of community building that has emerged between organizations grappling together to develop a shared understanding of an issue and an agreement around its strategic communication. Through an analysis of coalition structures and outputs, this article contributes to debates on transnational OCS coalitions by exploring the conditions for continuity, survival, and the generative properties of coalitions which move transnational civil society actors beyond purely ad hoc and instrumental, coordinated action to more durable identity-based forms of collaboration.