Starch digestibility is affected by a starch-protein matrix which limits digestion by rumen microbes. Therefore, disrupting this protein matrix is of great interest to dairy nutritionists. This study aimed to evaluate a commercially available processed corn product either intact or ground at various particles size on ruminal in situ DM and starch disappearance. Corn processing involved proprietary heat and pressure treatments that sheared the prolamin structure. Experiment 1 evaluated ruminal DM disappearance of processed corn (0Z45; patent #9,446,094; Matrix Nutrition LLC) either intact, cracked, or ground to pass through a 0.5, 2, or 4 mm sieve. A dry ground corn sample (ground to pass a 0.5 mm sieve) was used as a negative control. Ruminal in situ incubations were performed at 3, 6, 12, and 24 h to determine ruminal DM disappearance. Experiment 2 evaluated the kinetics of starch disappearance. Processed corn was either unground (intact) or ground to pass a 2 mm sieve. Ruminal in situ incubations were performed at 0, 3, 48, and 120 h to determine fractions A, B, and C of starch and the effective ruminal starch disappearance (ERD). Statistical analyses were performed using PROC Glimmix of SAS. For ruminal DM disappearance (Experiment 1), model included treatment, time, and their interaction as fixed effects, and the random effect of cow. For Experiment 2, fractions A, B, C, kd, and ERD were analyzed with fixed effect of treatment and random effect of cow. Overall, processed corn had greater (P < 0.05) DM disappearance than dry ground corn at 3, 6, and 12 h of incubation, but not at 24 h (P > 0.05). In addition, this effect was exacerbated with grinding or cracking (P < 0.05). Processed corn ground at 2 mm increased (P < 0.05) fraction A (42.5 vs. 17.9, % of starch) and ERD (62.7 VS. 40.8% of starch) and decreased (P = 0.001) fraction B (57.5 vs. 82.0% of starch) compared with the intact processed corn. These results indicate greater DM disappearance for processed corn compared with dry ground corn. In addition, reduced particle size improved ruminal starch disappearance of processed corn.