Under what conditions do cooperatively owned enterprises scale to stand alongside investor-owned firms? This article measures and attempts to explain large cooperatives’ variable prevalence across high-income capitalist democracies. Controlling for other known social, economic and geographic factors, statistical models confirm that state-mediated institutional arrangements, as operationalized through two comparative capitalism frameworks (Varieties of Capitalism and Welfare Regimes), are a significant factor in this variation. Cooperatives scale in a manner that complements arrangements in coordinated market economies, while exhibiting institutional incongruencies with those of liberal market economies and residual welfare states. Public policies which have variously enhanced or inhibited cooperatives’ ability to coordinate to scale are compared across four case countries (United States, France, Finland and New Zealand). Policy differences are shown to reflect the joint effect of state-mediated institutional arrangements alongside other control variables. They reveal how states privilege some ownership forms over others, suggesting a distinct political economy of ownership.