This paper examines the efficiency of a sample of Great Plains grain marketing and farm supply cooperatives during 1988 to 1992. In general, larger cooperatives were more X-efficient and scale efficient. Labor tended to be under-utilized and capital over-utilized. Petroleum product sales and fertilizer sales were negatively related to overall efficiency. Sales of goods other than grain, fertilizers, agricultural chemicals, petroleum products, and feed was positively related to overall efficiency. Overall efficiency was significantly correlated with the rate of return to assets.