Interest groups are key intermediary actors that communicate societal interests and preferences to public officials. Given public officials’ reliance on interest groups’ input in public policy processes, it is essential to understand how groups establish policy positions and assess the democratic nature of this process. Focusing on the leadership perspective, this article examines how interest groups involve their membership base in the process of defining their policy positions. The article relies on qualitative data from interviews with the leaders of interest groups active at the EU level and the statutes of these organizations. The findings show that the nature of policy issues under discussion and unequal resources of members lead to biased membership involvement in policy position-taking. While leaders are aware of these dynamics, their efforts to mitigate unequal participation seem limited, which raises questions about the representative potential of interest groups and the legitimacy of their policy claims.