Two randomized-block experiments were carried out to examine the relative value of wheat and barley as supplements to grass silage for finishing beef cattle. In each experiment unwilted, formic acid-treated silage was offered ad libitum and supplemented with 500 g soya-bean meal and 50 g minerals and vitamins to 44 12-month-old bulls for 157 and 172 days in experiments 1 and 2 respectively. Twelve of the animals also received 2·5 kg rolled spring barley (LB), 12 received 4·0 kg barley (HB) and 20 received 3·25 kg rolled wheat (W). For experiments 1 and 2 respectively the barley contained 796 and 787 g dry matter (DM) per kg; 118 and 105 g crude protein (CP) per kg DM; 47 and 57 g crude fibre per kg DM; the wheat contained 845 and 800 g DM per kg; 112 and 116 g CP per kg DM; 23 and 25 g crude fibre per kg DM; and the silages contained 190 and 177 g DM per kg; 153 and 176 g CP per kg DM; 80 and 104 g ammonia-nitrogen per kg total nitrogen. On average over the two experiments, for treatments LB, HB and W respectively, silage DM intakes were 5·4, 4·7 (s.e. 0·14) and 4·9 (s.e. 0·11) kg/day; total DM intakes 7·9, 8·3 (s.e. 0·14) and 8·1 (s.e. 0·11) kg/day; metabolizable energy intakes 91·4, 97·8 and 94·2 MJ/day; live-weight gains 1·04,1·19 (s.e. 0·029) and 1·10 (s.e. 0·023) kg/day and carcass gams 0·65, 0·77 (s.e. 0·017) and 0·70 (s.e. 0·013) kg/day. It is concluded that the feeding value of wheat was proportionately 0·98 of that of barley for finishing beef cattle when given as a supplement to grass silage, and that the type of cereal offered did not affect silage intake or carcass composition.