Public policy decisions are increasingly made by regional governance efforts that involve diverse decision makers from multiple government units within a geographic region. These decision-making bodies face competing pressures to represent regional and local interests. We study how decision makers balance preferences for regionalism and localism within metropolitan planning organizations (MPOs), the policymaking entities that are responsible for implementing U.S. federal surface transportation policy at the regional level. Our model of regional governance relates variation in regional policy outcomes to the incentives of MPO decision makers and the institutional environments in which they interact. Analyzing data from a sample of the nation's largest metropolitan areas, we find that MPOs dominated by elected officials produce more locally focused policies, holding other factors constant, while MPOs dominated by nonelected public managers produce more regionally oriented policies. Contextual factors, as well as the regional governance institutions themselves, further shape the balance between regionalism and localism.