Technical Abstract: Intake and digestion of pasture herbage can be influenced by canopy structure. A dual-flow continuous culture fermenter system was used to investigate the effect of forage species on digestion and ruminal fermentation. Four grass species [reed canarygrass (RCG), Phalaris arundinacea L; quackgrass (QG), Elytrigia repens; orchardgrass (OG), Dactylis glomerata, L.; and meadow fescue (MF), Festuca pratensis Hud.] were compared in a 4 x 4 Latin square design. Fermenters were sampled for pH, NH3-N, and VFA four times daily at each feeding (0700, 1030, 1430 and 2030 h). Effluent was analyzed for DM, CP, OM, purine concentration and bacterial production. The DM, OM, NDF, ADF, and CP digestibilities were calculated. Apparent DM, OM, and NDF digestibilities were not affected (P less than > 0.05) by forage species, averaging 39.2, 42.6 and 77.0%, respectively, across all forage species. Apparent ADF digestibility was least (P less than 0.05) for QG. True DM, OM and CP digestibilities were not affected (P greater than 0.05) by forage species, averaging 57.8, 60.0, and 83.0%, respectively. Mean, maximum and minimum rumen pH were not affected (P greater than 0.05) by forage species, averaging 6.212, 6.375, and 6.080, respectively. Total and individual VFA production and acetate to propionate ratio (A:P) were not affected (P greater than 0.05) by forage species with the exception of isobutyrate, which was greatest (P less than 0.05) for OG, and isovalerate, which was least (P less than 0.05) for MF. Total N intake was greatest (P less than 0.05) for OG and least for MF. The NH3-N production was greatest (P less than 0.05) for QG and least for MF. Total N and NH3-N flows (expressed as g/d) were greatest (P less than 0.05) for QG and least for MF. Efficiency of bacterial protein synthesis (gN/kd DM truly digested) was greatest for RCG and QG (P less than 0.05). The impact of individual forage species on ruminal fermentation is critical to gaining a better understanding of ingestive behavior for improved pasture management recommendations.