Mixed crop-livestock farming is often quoted as an agronomic ideal that is a source of savings for the farmer and has a lower negative environmental impact. The complementarity between livestock and crop units should allow the shared use of production factors, and thus a reduction in the use of inputs. Beyond the concept, the objective of this study is to observe whether, in a production area, farms producing beef and crops show different productive and economic performances from specialised beef cattle grassland farms. Based on data from a sample of Charolais suckler cattle farms in central France, we observe that the so-called mixed crop-livestock farms are systematically larger than specialised grassland farms. The large size of the farms leads to a strong increase in equipment needs and induced expenses. These expenses are not shared between animal and plant production. In the end, we do not observe any difference in production cost per kilogram of live-weight produced or in income per worker between specialised grassland farms and mixed crop-livestock farms. The virtuous concept of mixed crop-livestock farming comes up against structural and socio-economic realities. In order to be able to benefit from potential economic advantages linked to diversification, new forms of structure for French livestock farms should be considered.