As market conditions change rapidly in the 21st century, questions arise concerning how the organizational structures of co-operatives (co-ops) can meet the challenges that these new conditions pose. This paper introduces a framework to structure marketing co-ops (MCs) based on members' preferences. Several notions from the behavioral decision theory framework are utilized, and a principal-agent approach is adopted for the design of this framework. It focuses on the subjective utility that co-op members derive from levels of the MCs' firm-behavioral attributes, such as business issue/scope, corporate governance, product-related decision-making, financial structure, member benefits, and product quality. Data was collected by means of in-depth interviews with 30 producers and 120 structured computer-assisted face-to-face interviews. The utilities that producers attached to MC's attributes were derived by means of a conjoint experiment.