This paper describes how representative farm business models were employed to identify optimal beef and sheep production systems for Less Favoured Area (LFA) farms in Northern Ireland. The bio-economic models identify the optimal farming system for theses farms under various market and policy assumptions. They are useful, therefore, in helping to develop industry strategy. The models indicate that, under current market and policy conditions, a dairy-based beef system is likely to be the most profitable beef enterprise. However, depending on land quality and livestock housing resources, and the market and policy environment, suckler-based beef systems can also feature in the profit maximising enterprise mix. The results also suggest that the optimal sheep system is consistent with the stratified sheep systems traditionally operated in Northern Ireland. In general, beef production appears to have some advantages over sheep production where, depending on relative prices and resource availabilities, it is often better to replace sheep with cattle and employ the released labour off-farm, than to replace cattle with sheep and invest the released capital off-farm. In some situations, farmers should significantly reduce their capital and labour inputs to the farm business by substantially reducing stocking rates or even abandoning land completely