The objective of this study was to determine the effects of increasing inclusions of Diamond V Original XPC, a yeast fermentation product, on newly weaned beef steer performance and antioxidant defense. There was no effect of Original XPC on growth performance in the current study; however, blood measures indicated greater antioxidant capacity and lesser oxidative stress for steers fed XPC at 14 g/d. Further research is needed to better understand how oxidative stress impacts animal performance and health as well as the optimum supplementation dose of XPC for newly received beef cattle.