Two hundred forty beef calves (BW = 217 ± 20.6 kg) were used to evaluate performance, blood metabolites, and rumen development from feeding bermudagrass or ryegrass and rye baleage. Calves were stratified by BW, sex, and breed and assigned to one of 12 paddocks (0.40 ha each) with 4 treatment diets and fed for a 60 d backgrounding period. Diets included: early boot stage bermudagrass hay, (BERH); early boot stage ryegrass and rye baleage (ERRG); late bloom stage ryegrass and rye baleage, (LRRG); and early boot stage bermudagrass baleage, (BERB). Calves on BERH, LRRG, and BERB had free choice access to a 35% CP (as fed basis) liquid supplement. Body weights and rectal temperatures were collected on d -1, 0, 29, 30, 60, and 61 for comparison of BW, BW gain, ADG, and body temperature. Ruminal fluid and blood samples were collected for analysis of pH, NH3, VFA, PUN, and glucose from calves (n = 5 and 10/paddock, respectively) on d 0, 30, and 60. There was a treatment by day interaction (P < 0.01) for BW, temperature, PUN and ruminal pH. Body weights were heavier (P < 0.05) for LRRG compared with BERB and BERH, and heavier (P = 0.01) for ERRG compared with BERB on d 60, respectively. Body temperatures declined (P <0.01) from day 0 to 60. Plasma urea nitrogen was lowest (P <0.01) LRRG on d 30 compared with BERB and BERH; whereas, LRRG has the lowest (P <0.01) PUN on d 60 compared with the remaining treatments. Ruminal pH was lowest (P <0.01) for BERH and LRRG compared with ERRG on d 30, and highest (P <0.01) for ERRG on d 60 compared with BERB, respectively. Body weight gain and ADG were greater (P < 0.01) during the 60 d backgrounding period for calves fed ERRG and LRRG. A treatment effect existed for glucose where concentrations in the ERRG and BERH fed calves were greater (P <0.05) compared with the LRRG and BERB fed calves. A day effect for NH3 and glucose existed where concentrations decreased (P<0.01) from d 0 to 30 among all treatments. A treatment by day interaction existed (P =0.05) for butyrate where levels were greater for BERH and LRRG on d 30 compared with LRRG on d 60. Main effect of treatment (P <0.01) was observed for acetate and propionate, where BERB and LRRG had the lowest concentrations compared with ERRG and BERH. Performance of backgrounded calves fed ryegrass and rye baleage with or without supplementation, based on harvest stage, was improved over feeding bermudagrass hay with supplementation.