The food processing industry in Western countries operates in markets that usually are highly concentrated, consisting of a few cooperatives and investor-owned firms. However, in the literature some studies questioned whether the mixed market structure is a stable equilibrium, and suggestions are made that the cooperatives eventually will crowd out all investor-owned firms. To analyse the problem, the family of models of mixed markets is generalized and analysed. It is shown that a mixed market equilibrium may occur under quite general conditions. Also, it is shown that the investor-owned firm may serve as a yardstick of production to the cooperative, helping farmers achieve an increased payoff relative to a situation with a single coop in the market.