Thirty-five non-pregnant beef cows in three age classes (< 4 yr, 4–5 yr, and > 5 yr) were allocated at random to two treatments (fed, unfed) soon after weaning in November 1978. On day 1, the unfed group of 17 cows were marketed and the fed group of 18 cows were introduced to grain feeding. After 63 days, the fed cows were marketed and data were collected in a manner identical to those from the unfed cows. Feed consumption by the 18 cows in 63 days was 15 398 kg at a cost of $1 188.66. The cows gained a mean of 1.42 kg/day with an efficiency of 9.59 kg feed/kg gain. The < 4 yr, 4–5 yr and > 5 yr cows gained 1.59, 1.21 and 1.19 kg/day, respectively. Feeding produced significantly greater carcass weight, dressing percentage, fat depth and marbling scores (P < 0.01) and significantly (P < 0.05) greater rib-eye areas and brighter meat color. Carcass grade was also improved, resulting in a higher carcass price ($2.03/kg vs. $1.93/kg) and, combined with carcass weight, a significantly (P < 0.01) greater total carcass value. Feeding caused a greater incidence of liver abscesses (50% vs. 29%), but reduced the incidence of yellow fat (0% vs. 29%). Under the economic conditions at the time of the study, it was profitable to feed all age classes of cows. The conditions under which grain feeding of cull cows would be profitable are discussed.