"Canadian milk marketing boards are agricultural institutions tightly linked to the administration of dairy programs and supply management. Using insights from the New Institutional Economics (NIE) literature this paper investigates the factors influencing the emergence of these self-regulated, "hybrid" institutions that are managed by producers but necessitate governmental intervention to be operational. Our analysis focuses on the case of the Québec milk marketing board. It shows that the Québec milk board ensured transactional security among trading partners, where neither pure private ordering contract enforcement institutions, nor pure public ordering institutions would have succeeded to do so. The empirical case of the Québec milk board thus suggests that marketing boards in Canada may have historically assumed a broader function than merely increasing producers' rents." Copyright (c) 2008 Canadian Agricultural Economics Society.