We developed a simple model predicting dry matter intake and diet digestibility at pasture, for a simulator of grassland-based suckler systems. Herbage is divided into structural components described by their biomass and digestibility. Diet composition is calculated assuming that the most digestible and abundant components are preferred. Dry matter intake depends on diet digestibility, animal intake capacity (function of animal characteristics), and sward biomass. The model is sensitive to digestibility of herbage components. Its predictions were satisfactory, since error represented 5% of the mean observed value for diet digestibility and 10% for the dry matter intake.