While distillers dried grains (DDG) may be a plentiful energy and protein supplement, it is necessary to understand how this feed affects the intake and digestibility of forages.  In fall, 2006, a digestion trial was conducted to evaluate the effects of feeding increasing amounts of DDG on DMI, and digestibility of smooth bromegrass hay. Three steers (737 lb) were placed in metabolism stalls in an environment controlled room and fed smooth bromegrass hay with DDG at 0, 0.5, 1.0 and 1.5% BW in successive periods. Each period consisted of a 10-day adjustment and a 5-day collection period.  During the adjustment and collection periods, smooth bromegrass hay was fed at 110 and 100% of ad libitum intake, respectively with water available at all times. During collection, feeds, total feces, and urine were collected and sub-sampled. Three days for rest and acclimation to the new diet were provided between each period. With increasing levels of DDG, total DMI were 9.3, 11.6, 12.8, and 15.7 lb/day for steers fed DDG at 0, 0.5, 1.0, and 1.5% BW, respectively (P=0.0001). The substitution rate of DDG for smooth bromegrass hay (lb hay/lb DDG) was: y=-0.0017 + 0.9812x -0.4582x² (r² = 0.76), where x was the DDG intake, as a percentage of BW in the diet.  Dry matter digestibility of diets in which DDG were fed at 0. 0.5, 1.0, and 1.5% BW were 54.9, 63.6, 65.8, and 67.0 (P=0.001) and were predicted as: y = 59.6 + 15.76x -6.389x² where x was the DDG intake, as a percentage of BW. Total digestible dry matter as a percent of BW was 1.7 on average, not differing significantly over treatments (P=0.26). The supplementation of DDG to steers fed smooth bromegrass hay increased total DM digestibility of consumed feed while increasing the total feed intake.