To increase the profitability and sustainability of beef production systems, the use of animals with high feed efficiency is preferred. Efficient animals eat less than their peers for the same or better growth. This efficiency can be measured using feed conversion ratios (FCR) and residual feed intake (RFI) parameters. However, the biological mechanisms, particularly those related to the animal’s behaviour and personality, are poorly understood. An individual animal’s behaviour, such as its activity levels, may contribute to efficiency. Feed intake is also a factor in efficiency, and therefore, social dominance rank may also indirectly affect efficiency through its influence on feeding behaviour. This experiment investigated the effects of dominance on feeding behaviour, as well as of dominance and activity on average daily gain (ADG), FCR and RFI in two breeds of beef cattle. The study used a 2 × 2 design with 80 cattle of two breed-types (Charolais-cross (CHx) (n = 41) and Luing (n = 39)) and two diets (a concentrate-based diet (CONC) and a mixed forage and concentrate diet (MIXED)). For each individual steer, FCR and RFI were measured over a 56-day performance test. Feed intake, patterns of feeding behaviour, activity and dominance were also measured. Feed intake was affected by dominance, with more dominant steers having significantly higher dry matter intakes (P = 0.001) and feeding rates (P = 0.006) suggesting that dominant animals had priority of access to the feeders. Steers with higher ADG had higher intakes and performed more standing bouts. Steers with better FCR values performed more standing bouts and younger animals had better FCR. For RFI there was also an interaction between breed and variation in length of the feeding events, showing that Luing steers with more consistent feed bout lengths had better RFI, with no association shown for CHx steers. There was no direct effect of dominance on ADG, FCR or RFI. However, the effect of dominance on feed intake suggests that measures of performance in any study may be affected by feeder-space allocation. The associations between standing bouts and feeding bouts with efficiency measures also suggest that individual animal behavioural characteristics influence efficiency and that overall efficiency of all animals may be improved by allowing animals to express individual patterns of behaviour.