Stakeholder negotiation is an increasingly important policymaking tool. However, relatively little is understood about the relationship between the structure of the negotiating process and the effectiveness with which participating stakeholders can pursue their individual interests. In this paper, we apply the Rausser-Simon multilateral bargaining model to a specific negotiation process, involving water storage capacity and use in the upper part of the Adour Basin in south-western France. The richness of the data and institutional information available to us provides a realistic environment in which to examine the effect of negotiation structure on participant power. We focus in particular on the three farmer stakeholder groups. Because their interests are aligned but distinct, they form a natural negotiating coalition. We construct experiments that enable us to evaluate the effects of negotiation structure on the effectiveness of this coalition. Our comparative statics experiments highlight a number of aspects of the relationship between negotiation structure and bargaining power. In addition to the standard indices of bargaining power—the distribution of access and players’ utilities in the event that negotiations break down—our analysis identifies a number of other, less obvious, sources of power. First, we show that a coalition member may obtain a better bargaining outcome when his access is reduced, if the redistribution increases the access of another coalition member who has a more favorable “strategic location.” Second, we show that the interests of the coalition as a whole will usually, but not always, be advanced if its members cede access to a “spokesman” representing their common interests. However, some coalition members may be adversely affected. Third, we consider the effect on the coalition of restricting the set of proposals that may be placed on the bargaining table. In particular, we impose increasingly tight restrictions on the extent to which coalition members can make bargaining proposals that further their own individual interests at the expense of the interests of other coalition members. We find that usually, but not always, such restrictions harm the coalition as a whole.