The core executive is a central focus for the study of policy change especially in Westminster-style parliamentary democracies such as the UK. This venue is recognised as the locus of power and where attention should be given for identifying and assessing the process of policy change. It is surprising, then, that studies on women's substantive representation - showing whether and how women can make a difference to politics and policy - have not examined this institution, focusing instead on parliament or women's policy agencies. We plug this gap in scholarship in suggesting that the core executive should be the key venue for examining substantive representation of women. At the same time we present the case that the core executive is a gendered institution in terms of recruitment, resource allocation, relationships and rules. We argue that this gendered disposition shapes the opportunities and constraints available to feminist actors intent on altering the gender emphasis of public policy and illustrate this empirically through a case study of the actions and successes of two feminist ministers - Harriet Harman and Patricia Hewitt. As such this article makes a contribution to mainstream core executive research, gender and politics scholarship as well as the new and feminist institutionalist literatures. © 2010 The Authors. Political Studies © 2010 Political Studies Association.