How does public participation in agency policymaking affect bureaucratic administration, policy outcomes and democratic governance?  Specifically, how can government agencies structure public participation to include diverse expertise in the policymaking process and yet avoid privileged influence and possible corruption? To address these puzzles, I examine the vast US system of federal advisory committees over the 50-year span between 1962 and 2012 and provide a close look at public participation in pharmaceutical regulation.  Using a unique dataset of participation through public committees advising the Food and Drug Administration’s Center for Drug Evaluation and Research, my paper assesses the expertise, experience, and deliberative contributions of nearly 1000 individuals participating in over 200 meetings for New Molecular Entities reviewed between 1988 and 2009.  This paper demonstrates the organizational attributes and conditions that enable public committees to negotiate democratic tensions in bureaucratic settings.  Broadly, the results suggest that public committees offer portals of democracy into bureaucratic policymaking when participants reflect diverse expertise and have opportunities for sustained engagement on discrete policy tasks. Specifically, the results suggest public participation can contribute to improved policy outcomes, such as safer drug products, when participants’ financial conflicts of interest are limited or minimal.  To support improved policy outcomes, however, restrictions on participation designed to discourage conflicts of interest must nonetheless uphold standards of diverse expertise and opportunities for sustained engagement. In contrast to proposals and policies that call for government bureaucracies to emulate private organizations and businesses, participatory bureaucracy provides a public model for effective government administration.