Glanc, D. L., Campbell, C. P., Cranfield, J., Swanson, K. C. and Mandell, I. B. 2015. Effects of production system and slaughter weight endpoint on growth performance, carcass traits, and beef quality from conventionally and naturally produced beef cattle. Can. J. Anim. Sci. 95: 37-47. Effects of production system and slaughter endpoint on performance, carcass traits, and beef quality were investigated in 64 Simmental cross steers (minimum 75% Continental breeding). Cattle were allocated to: (1) conventional production system based on use of implants and dietary ionophores or (2) natural production system in which no implants or ionophores were used. Within each production system, cattle were allocated for slaughter at 545 or 636 kg liveweight. Steers were fed an 85.5% concentrate diet based on high-moisture corn, soybean meal, and alfalfa silage. Average daily gain tended to be greater (P<0.06) in conventional production system cattle, while there was a trend (P<0.08) for production system by endpoint interactions for dry matter intake and gain to feed. Natural production system cattle tended to have greater (P<0.08) marbling and percent intramuscular fat (%IMF) with lower (P<0.09) longissimus shear force, while production system by endpoint interactions were present (P ≤ 0.03) for%IMF and carcass lean composition via rib dissection. At-home consumer evaluation of longissimus muscle steaks found tenderness, juiciness, flavour, and overall acceptability rankings were greater (P<0.01) for steaks slaughtered from heavier cattle (636 vs. 545 kg liveweight). Marketing cattle at lighter slaughter weights may have benefits for performance at the expense of eating quality.