A model was developed to simulate production of wheat and stocker cattle. A mechanistic plant model (CERES-Wheat, Ritchie & Otter, 1985) was combined with empirical equations for animal intake and growth to produce a Wheat Grazing Systems model, called WGS. Grazing reduces the plant's leaf area index which affects the ability of plants to fix energy, the rate of evapotranspiration, the rate of soil water evaporation, and the rate of leaf senescence. Grazing also reduces the accumulation of aboveground biomass in the average wheat plant; thus, affects the rate of ear growth, grain filling, and, ultimately, grain yield. Simulations using daily weather data showed that forage biomass and grain yield decreased as grazing intensity increased. Observed and pridicted forage biomass and grain yield were correlated with an r 2 of 0·63 and 0·74, respectively. Simulations using daily weather data showed that the WGS model predicted observed intraseasonal live animal weight gains with an r 2 of 79%.