Cooperatives are organized to be democratic. However, large membership size can create problems for democratic process and governance. Attending meetings and casting votes may not be enough to preserve democratic characteristics. This report develops a set of propositions-a theory-for structuring membership to improve democratic opportunities and responsiveness. Aspects of these propositions are tested against data from dairy herd improvement cooperatives in Wisconsin and are supported. These propositions suggest potential structural design options, given specific stressors in the membership environment, and the management and operations environment.