The hypothesis that inclusion of a rumen-inert fat in the diet of dairy-origin bulls would enhance EUROP carcass fat classification and tissue fatty acid composition was tested. Sixty bulls (age = 508 days, s.d. 29.1) were offered ad libitum, a barley-based concentrate ration that contained 0, (control) 26 (MEGA1) or 81 g (MEGA2) calcium salts of palm oil fatty acids (Megalac)/kg such that the rations contained 25, 49 and 116 g acid-hydrolysed ether extract /kg dry matter (DM), respectively. Intake (per pen of 5 bulls), live weight and ultrasonic backfat thickness were measured during a 130 day feeding period after which bulls were slaughtered, carcass characteristics recorded and a sample of longissimus muscle (LT) and subcutaneous adipose tissue (SAT) collected for fatty acid analysis. Subcutaneous fat depth was similar for control and MEGA1 bulls but lower (P < 0.05) for MEGA2 bulls after 60 days of the study. After 125 days, compared to control bulls subcutaneous fat depth was higher for MEGA1 bulls but lower for MEGA 2 bulls (P < 0.05). Carcass gain tended (P = 0.074) to be lower for MEGA2 bulls compared to control and MEGA1 bulls, which reflected their lower consumption of concentrate DM and metabolisable energy (ME) but the efficiency with which consumed DM or ME was converted to live or carcass weight did not differ significantly between rations. There was no difference between control and MEGA1 bulls for any measurement of carcass fatness. Compared to control and MEGA1 bulls, carcasses from MEGA2 bulls were lighter, had a lower depth of fat covering the LT muscle measured post-mortem (P < 0.05) and a numerically lower carcass fat classification. There were only minor effects of ration composition on the fatty acid profile of LT or SAT. With regard to nutritional indices in meat, compared to control bulls, inclusion of Megalac did not affect the polyunsaturated (P) to saturated fatty acid ratio or the n-6 to n-3 P ratio of tissue lipids. It is concluded that for the type of animal and feeding arrangement in this study, rumen inert fat inclusion was not an effective strategy to enhance carcass fat classification or the nutritional value of beef.