Carcass and eating quality characteristics of crossbred wether and female lambs sired by Charollais (C), Suffolk (S) and Texel (T) rams out of Mule ewes (Bluefaced Leicester ♂ × Scottish Blackface ♀ or Swaledale ♀) were evaluated in a study carried out over a 3-year period in an upland flock. A total of 10 unrelated rams of each breed were used as sires. Lambs (no. = 280) were selected for slaughter at the same estimated subcutaneous fat level on four occasions within each year (i.e. at weaning in July and at approx. monthly intervals thereafter). Following slaughter, the left side of each carcass was physically dissected. A loin joint from lambs slaughtered in the 2nd and 3rd years of the study (no. = 184) was used to evaluate eating quality. Suffolk-sired lambs were heavier at slaughter (S: 42.2; C: 41.0; T: 40.7 (s.e. 0.35) kg) but had similar killing-out proportions compared with the other two breeds (S: 444; C: 450; T: 452 (s.e. 26) g/kg). Texel-sired lambs had higher lean proportion (S: 543; C: 550; T: 567 (s.e. 4.4) g/kg) and lower total carcass fat proportion (S: 240; C: 242; T: 233 (s.e. 5.3) g/kg) compared with S and C sired lambs. Bone proportion was similar for C and T lambs but was higher for S (S: 199; C: 191; T: 191 (s.e. 2.1) g/kg). Lean : bone (S: 2.75; C: 2.90; T: 2.99 (s.e. 0.037)) and lean :fat (S: 2.38; C: 2.40; T: 2.54 (s.e. 0.034)) ratios were higher for T-sired lambs. Female lambs were lighter (40.4 v. 42.2 (s.e. 0.24) kg), and had proportionately more intermuscular fat than wethers (122 v.118 (s.e. 1.3) g/kg) but the sex differences for other tissue proportions were small Carcass weights and total carcass fat proportions increased and lean proportions decreased across the four slaughter dates. There were no effects of breed or sex on eating quality. However, samples from lambs slaughtered at weaning were judged to be more tender than those slaughtered later in the season.