Technical Abstract: The growing ethanol industry in the Southern Great Plains has increased the use of wet distiller's grains with solubles (WDGS) in beef cattle finishing diets. Few studies have used steam-flaked corn (SFC)-based diets to evaluate the effects of WDGS in finishing cattle diets, and a reliable estimate of the net energy value of WDGS has yet to be determined. Effects of corn processing method and WDGS on energy metabolism, carbon (C) and nitrogen (N) balance, and enteric methane (CH4) production were evaluated in Jersey steers using respiration calorimetry chambers. A 2 x 2 factorial arrangement of treatments was used in a Latin square design. The factors consisted of corn processing method (SFC or dry-rolled corn [DRC]) and inclusion of corn-based WDGS (0 or 30% on a DM basis). Thus, the four treatment combinations consisted of: (1) SFC-based diet with 0% WDGS (SFC-0); (2) SFC-based diet with 30% WDGS (SFC-30); (3) DRC-based diet with 0% WDGS (DRC-0); and (4) DRC-based diet with 30% WDGS (DRC-30). Diets were balanced for degradable intake protein (DIP) and ether extract (EE) by the addition of cottonseed meal and fat. As a proportion of intake energy (IE), grain processing method did not affect (P > 0.12) fecal, digestible, urinary, and metabolizable energy, or heat production. Steers consuming SFC-based diets produced less (P < 0.04) CH4 than steers consuming DRC-based diets. Retained energy tended to be greater (P = 0.09) for cattle consuming SFC- than DRC-based diets. Inclusion of WDGS did not affect (P > 0.17) fecal, digestible, urinary, metabolizable, and retained energy, or heat production as a proportion of IE. Due in part to greater N intake, cattle consuming diets containing 30% WDGS excreted more (P = 0.01) total N and excreted a greater (P < 0.01) quantity of N in the urine. From these results, we conclude that cattle consuming SFC-based diets produce less CH4 and retain more energy than cattle fed DRC-based diets; however, dietary inclusion of WDGS at 30% seems to have little effect on CH4 production and energy metabolism when diets are balanced for DIP and EE. Additionally, cattle excrete a greater amount of C when fed DRC- compared to SFC-based diets, and dietary inclusion of 30% WDGS increases urinary N excretion when diets are balanced for equal DIP concentration. Under the conditions in our experiment, the net energy (NE) values of WDGS are greater than the NE values of SFC or DRC, and the NE values are similar when fed in both SFC and DRC-based diets.