Normal (N, n=11) and heavy muscled (HM, n=9) lambs were produced from Polypay dams and Dorset sires heterozygous for the Callipyge (CLPG) gene to study the effects of the gene on live body weights, carcass and meat parameters. Lambs were grown as a single group on a high energy diet to a target slaughter weight of 57 kg. Live body weights were recorded monthly from birth to pre-slaughter. At slaughter, kidney and pelvic fat were recorded and two muscles, biceps femoris-caudal (BFC) and semitendinosus (ST), were removed, weighed, and used for other studies. Carcasses were sectioned between the 12th and 13th vertebrae for determination of ribeye area (REA) and fat depth over the loin and lower rib. Two additional muscles, biceps femoris-major (BFM) and semimembranosus (SM), and four loin chops cut 2.5 cm thick were removed from each carcass, sealed in Cryovac wrap, and frozen for later cooking. HM lambs had greater REA (23.0 vs. 13.6 cm 2; P<0.01), less fat ( P<0.01 for all measures), and greater weight of all dissected muscles (all P<0.01 except BFC for which P=0.13). Chops were cooked by grilling and the leg muscles were individually wrapped in aluminum foil and roasted whole, all to an internal temperature of 70 °C. HM carcasses produced higher Warner–Bratzler shear values for longissimus muscle (4.7 vs. 2.2 kg, P<0.01), but no significant differences were detected for BFM (2.6 vs. 2.5 kg) or SM (4.9 vs. 4.5 kg). The two genotypes did not differ in either percent cooking loss or percent moisture in the cooked meat from any of the three muscles.