Why do committees exist? The extant literature emphasizes that they pool dispersed information across members. In this paper, we argue that they also may serve to discourage outside influence or capture by raising its cost. As such, committees may contain members who are uninformed or else add no new information to the collective decision. We show that the optimal committee is larger when outsiders have larger stakes in its decision, contribute lower quality proposals, or when its members are more corruptible. We also show that keeping committee members anonymous and accountable for their votes help deter capture.