Experiment 1 compared chemical composition and disappearance kinetics of loose and extruded dried distillers' grains (DDG), as well as evaluated DDG cube supplementation rate on DMI and digestibility for growing cattle consuming ad libitum bermudagrass (Cynodon dactylon) hay. Charolais-cross heifers (n = 23) received either no supplement, or DDG at 0.90, 1.81, or 3.62 kg/d. Extrusion increased (P </= 0.01) fat and TDN, immediate solubility and effective degradability of DDG DM, and decreased (P </= 0.01) NDF and ADF. Increased supplementation linearly and quadratically decreased (P < 0.01) hay DMI and DMD, respectively, but linearly increased (P </= 0.01) total DMI and DMD. Each year of experiment 2 (year 1 = 155d, year 2 = 182d), 140 steers were randomly assigned to 1 of 9 tall fescue (Festuca arundinacea)/bermudagrass pastures (7.2 +/= 2.90 ha) to evaluate DDG cubes on forage and steer performance, and profitability. Treatments (n = 3 pastures/treatment) included: 1) Fertilized Control (FC), no supplement/fertilized pastures; 2) Fertilized Supplement, 3-d/wk fed 2.9 kg DDG/fertilized pastures; or 3) Supplement (S), 5-d/wk fed 0.75% BW/d DDG /unfertilized pastures. Biomass was greatest (P < 0.01) in September both years. Fertilization increased (P < 0.01) CP and decreased (P </= 0.02) ADF and NDF relative to S in early summer. Supplemented animals had heavier (P </= 0.01) mid-summer and final BW than FC. Late and total gains were greater (P < 0.01) for S than FC and FS. Supplementation had greater (P < 0.01) cost of gain and gross returns, but least (P < 0.01) net returns. Experiment 3 used year 1 steers to evaluate carryover effects of supplementation on feedlot performance and carcass characteristics. Supplemented animals required fewer DOF (P < 0.01) than FC, and DMI and feed costs were lower (P < 0.01) for S than FC and FS. Gains were greater for FC and FS from d0-84 (P = 0.02) than S. At harvest, FC had lower YG (P = 0.01) than FS, and greater DP (P < 0.01) than supplemented animals. There were no differences in harvest BW (P = 0.23) or other carcass characteristics (P >/= 0.17).