Abstract The abundance of craft breweries provides widespread availability of wet brewers grains (WBG) to be used by beef cattle producers as a potential feedstuff. Cotton gin byproduct (CGB) is a feedstuff typically reserved for mature beef cows due to its low and variable feed value. Both WBG and CGB have high cost of transportation but are sometimes used by producers near supply centers due to their low price. The objective of this study was to analyze animal performance of growing Angus steers fed total mixed rations with varying amounts of CGB and WBG. Sixty-four Angus steers (365 ± 26 kg) were allotted and blocked by initial body weight (BW) in a randomized complete block design to 8 dietary treatments and fed in 2 phases, growing phase (GP) and finishing phase (FP) (84-d and 69-d, respectively). Dietary treatments were arranged in a 2 x 4 factorial with two levels of CGB (0 or 25% of DM) and 4 levels of WBG (0, 10, 20 or 30% of DM). The control and base of all treatments were corn, corn silage and soybean meal. Body weights were recorded on two consecutive days at the beginning and end of GP and FP. Feed samples were collected, and refusals were weighed weekly. Data were analyzed using the MIXED procedure of SAS 9.4 with main effects of CGB, WBG, and the interaction. The linear, quadratic, and cubic effects of increasing levels of WBG and CGB were tested with polynomial contrasts. Average daily gain (ADG) did not differ among dietary treatments (0, 25% CGB and 0, 10, 20, 30% WBG) for GP, (1.67, 1.61, and 1.67, 1.57, 1.74, and 1.60 kg/d, respectively) (P > 0.3031), FP (1.53, 1.61 and 1.56, 1.53, 1.61, and 1.58 kg/d) or the overall trial (1.61, 1.62 and 1.62, 1.55, 1.68, and 1.60 kg/d). The addition of CGB increased GP dry matter intake (DMI; 11.06 vs 11.99 kg/d; P = 0.0011), while the addition of WBG linearly decreased GP DMI (11.81, 11.69. 11.81, and 10.81 kg/d; P = 0.0292). There was an interaction between CGB and WBG (P = 0.0206), with increasing levels of WBG at 0% CGB exhibiting a cubic effect (P = 0.0127), but no effect at 25% CGB. Inclusion of CGB decreased feed efficiency (FE) in the GP (6.77 vs. 7.69; P = 0.0008) but had no carry-over effect in the FP. There was no effect of WBG on FE in GP or FP. In conclusion, CGB increased DMI, reduced FE, and maintained ADG. Increasing quantities of WBG did not reduce ADG or FE, but decreased DMI with increasing feeding level. Therefore, WBG and CGB can be considered viable options for cattle producers seeking to lower input costs.