Knowledge of the spatio-temporal management of forage production and grazing in grass-based livestock systems is needed to simulate their functioning and then to propose new cutting and grazing practices that will achieve both environmental and economic benefits. The objectives of the present work were to characterize the types of grassland use in mountain bovine systems and relate them to field geographical characteristics to produce a conceptual model of grassland use. This model can be incorporated into a whole beef and/or dairy farm simulator of the impact of practice changes on environmental and productive performances. For this purpose, a survey of 72 farms was conducted in the traditional Salers system in the Massif Central (France). Information was gathered on geographical characteristics and cutting and/or grazing practices on three general groups of fields: cut only, cut and grazed, and grazed only fields. Principal component and hierarchical cluster analyses constructed 15 field use classes that account for the complexity of forage production and grazing management. Geographical determinants of grassland use follow a certain hierarchy: slope and carrying capacity influence the occurrence of cutting, and field area determines the possibility of allocating a cut field to grazing animals and of allocating a field to milked cows. The distance to the cowshed is involved in the allocation to milked or suckler cows and also influences the order of the cutting and grazing sequence. For the same combination of geographical characteristics, two types of grassland use may be observed, highlighting the flexibility of mountain systems. A conceptual model of grassland use is proposed as the basis for field use allocation in a whole farm model. Further investigation will consider the influence of field pattern characteristics on these relationships.