This article shows how a philanthropic organization, Open Society Foundations (OSF), contributes to building the fight against discrimination as an organizational field within the European institutional sphere. OSF operates according to a strategy already studied in the case of other foundations : through “enrolling” different grantee organizations into a collective project. However, OSF is a specific case because of its direct intervention as a protagonist of the field, either as part of coalitions with NGOs, or in its own name as a lobby in the EU arena. OSF is indeed a hybrid actor : it is a grant-maker with considerable resources in a time of increasing scarcity of public funding, but it also acts as a think tank and a lobby, basing its public policy proposals on both the expertise of highly qualified employees and on the knowledge provided by its grantees. Therefore, OSF differs from the model described in the literature of philanthropic organizations which indirectly and “subtly” shape social movements and their organizational fields.