An expanding body of research demonstrates that high quality early childhood education and care (ECEC) programmes generate positive outcomes for children; in response, policy makers in a number of countries are making significant programme investments. No research consensus, however, has emerged around the specific types of policy intervention that are most effective. Much remains to be clarified in terms of specific policy interventions that flow from the evidence base. To respond to these important gaps in ECEC knowledge, we advance a call for a research agenda that will systematically examine the effects of early years policy instruments and settings.