Because treatment with calcium oxide (CaO) will increase the digestibility of corn stover, CaO-treated corn stover may be a cost-effective alternative to a portion of corn grain in beef feedlot diets. Single-pass harvested corn stover was ensiled either untreated or treated with 5% CaO on a dry matter (DM) basis. Ground baled stover, untreated stover silage, or CaO-treated stover silage were fed at 20% of the diet DM with modified distillers grains with solubles and corn grain at 40 and 35% of the DM and fed either during the growing phase or both the growing and finishing phases in comparison to a control diet containing baled stover, modified distillers grains with solubles, and corn grain at 5, 20, and 70% of the diet DM. The DM digestibilities of diets fed to sheep that contained the baled stover, untreated stover silage, and CaO-treated stover silage diets were 75.9, 75.5, and 83.2%, respectively. In the beef feeding trial, 210 steers (30 per treatment; mean weight 648 lb) were either fed the control diet to finish or fed the baled stover, untreated stover silage, CaO-treated stover silage diets for either the growing phase to 1,000 lb or to finish. Daily gains of steers fed the control treatment or the CaOtreated stover silage diet were greater than steers fed the CaO-treated stover silage diet during the growing phase or untreated stover silage diet to finish which were greater than steers fed the baled stover silage diets to finish or the untreated stover silage during the growing season. Steers fed the CaO-treated stover silage diet to finish had a lower feed-to-gain ratio than any other treatment. Steers fed the control treatment had a higher marbling score than those fed diets containing any of the corn stover treatments. Calcium oxide treated stover is a cost-effective replacement for a portion of the corn in feedlot diets.