Corn stover treated with alkaline and pelleted with protein may lower feed costs and partially replace a variety of concentrate feeds in dairy cow diets. The objective was to evaluate treated corn stover pelleted with different sources and processing of protein feedstuffs on lactation performance and rumen characteristics. Twenty lactating Holstein cows were enrolled in a multiple 5 × 5 Latin square design with 21-d periods and randomly assigned to 1 of 5 treatments: (1) control diet with no pellets (CON), (2) treated corn stover with extrusion processed soybean meal pellets, (3) treated corn stover with unprocessed soybean meal pellets, (4) treated corn stover with extrusion processed dried distillers grains with solubles pellets, and (5) treated corn stover with unprocessed dried distillers grains with solubles pellets. All diets were formulated to contain 53.5% forage and 46.5% concentrate (DM basis). For pellet diets, inclusion rate was maintained at 20% (DM basis) and replaced 40% ground corn, 32.5% canola meal, 25% soybean hulls, and 2.5% limestone. Data were analyzed using the MIXED procedure of SAS. Dry matter intake (DMI) was greater (P < 0.001) for cows fed CON diet (30.8 kg/d) than cows fed pellet diets (27.1, 26.4, 26.2, 26.5 kg/d). Cows fed CON diet were greater (P < 0.001) in milk yield compared with cows fed pellet diets (47.5 vs. 42.4, 42.7, 43.0, 42.8 kg/d). However, DMI and milk yield did not differ for cows fed the pellet diets (P > 0.10). Milk fat and lactose percentages were unaffected (P > 0.10) across all 5 treatments, while cows fed CON diet produced greater milk protein percentage than cows fed pellet diets (P < 0.001). Feed efficiency (energy-corrected milk/DMI) tended (P = 0.08) to increase for cows fed pellet diets compared with cows fed CON diet. There were no differences in total ruminal VFA for cows fed CON vs pellet diets (P > 0.10), however; protein processing decreased ruminal acetate and increased propionate percentages (P < 0.01). At 20% inclusion rate in the diet, there does not appear to be an advantage of one pellet over the other in terms of performance.