Supplementation of a zinc-amino acid complex (ZnAA)at 60 ppm increased carcass-adjusted final BW, ADG, and improved F:G of cattle fed Optaflexx (OPT) when compared with cattle fed OPT alone. Under the conditions of this study, steers fed OPT for 28 days had a 0.9%increase in HCW relative to non-OPT cattle that was improved to 2.1% greater in steers supplemented with ZnAA and OPT. Zinc supplementation without OPT did not affect performance. In addition, ZnAA supplementation didnot extend the response to OPT, as the performance of steers receiving OPT for 28 or 42 d was not different in Zn supplemented steers. There appears to be a synergy between Zn and OPT supplementation that leads to improved finishing steer performance, although the mechanism is currently unknown.