This article investigates competing visions of how regional organizations influence cooperation among individual local governments within a metropolitan area. As network brokers among local governments, regional organizations can reduce the transaction costs of self-governing solutions to regional problems through bargaining and contracting among local units, but their centralized activities might also crowd out interlocal exchanges. Florida Regional Planning Councils are examined to test competing hypotheses based on these two visions, identifying the influence of regional organizations’ governance and activities on interlocal revenue transfers among municipal governments. Evidence that regional organizations can complement as well as substitute for interlocal cooperation is reported. In conclusion we discuss these findings in the context of vertical and horizontal federalism and theories of institutional collective action.