The efficient production of lean beef suitable for current consumer demand necessitates effective rationing of beef cattle. Feeding standards for beef cattle given by ARC (1980) predict that a reduction in energy intake produces a large reduction in performance with little effect on the energy or fat contents of the gain. However previous studies have shown that diets containing a high proportion of grass silage may sustain lower levels of performance and result in a greater proportion of fat in the gain in both calves and finishing cattle, than when similar quantities of energy and protein are given in the form of high-concentrate diets. The effects of a change in energy intake on performance and carcass composition of beef cattle are therefore likely to depend on whether this change is achieved by restricting the quantity of food given or changing the forage: concentrate ratio of a diet given ad libitum.The present experiment was carried out to examine the effects of forage:concentrate ratio in the diet and ad libitum versus restricted dry matter intake on the performance, carcass composition and efficiency of lean meat production by steers.