Recently a large amount of research has focused on the relationship between forage species richness and dry matter (DM) yield. However, little research has focused on the economic impact of forage mixture complexity on a whole farm scale. In this study the Integrated Farm System Model (ISFM) was used to assess the economical impact of thirteen forage mixtures ranging from 2- to 9-species in a whole farm scenario. The yield and quality of the forage mixtures were evaluated under grazing for three consecutive growing seasons (2002-2004) near State College, Pennsylvania. The IFSM pasture sub-routine was modified to use the DM and quality data from the grazing experiment to simulate the net return of two contrasting dairy farms. One of the simulated farms represented a grazing based dairy, where all animal categories graze year-round. The second farm represented a "typical" dairy farm of Pennsylvania with the exception that all animals grazed half days during the growing season. The results of these simulations showed that the maximum net return was reached in the grass based farm and the typical farm when using a two-species mixture ($101 600) and a six-species mixture ($75 500), respectively. In both farms total forage DM explained 96% and 75% of the variation in net return for the grass based and typical farm, respectively. This may be due to the fact that the overall quality of the forage mixtures was adequate for milk production. This analysis reveals that multi species forage mixture could be economically viable in conventional dairy farms. Additionally, when comparing forages with high nutritional value; DM production is the driving mechanism to maximize net return.