Supplementation of 60 ppm Zn from Availa®Zn improved performance during the initial 86 days of the 115 d finishing period. However, during the final 29 d, when Optaflexx (OPT) was included in the diet, increasing concentrations of Availa®Zn linearly increased growth of OPT-fed steers. During this period supplementing 90 ppm of Zn had the greatest additive effect on the response to OPT, suggesting that the addition of Zn to OPT diets may improve performance.