We evaluated effects of enzymatically hydrolyzed yeast (EHY) and supplementation frequency (FREQ) on immune parameters among beef cows and calves. Eighty multiparous (parity = 4.2 ± 0.3) cows were fed a common brome hay-based diet (CP = 8.0 ± 0.1%). Cows were blocked by expected calving date and stratified by BCS within block before random assignment to treatment. Beginning 88 ± 5 d prior and up to parturition, cows were provided 1 kg daily or 3 kg every 3 d of a soybean hull-based supplement that contained 0 or 3 g/kg EHY. The daily supplement was designed to meet ruminal N requirements. Cows were vaccinated against rotavirus at 62 and 48 ± 5 d before parturition. Jugular blood was collected from cows at 62, 48, 40, 24 and 14 d before parturition. At parturition, colostrum was milked from cows before feeding to calves and jugular blood was collected from cows and calves. Subsequently, calf plasma was collected at 2 and 14 d after parturition. Calf plasma IgG concentration increased (Quadratic < 0.01) as age increased and the passive transfer status among calves was ‘excellent’ (i.e., calf 2 d plasma IgG = 37 ± 1.9 g/L; APHIS, 2010). Nonetheless, plasma IgG was greater (P = 0.03) among calves born to cows supplemented EHY; FREQ had no effect on plasma IgG in calves. Despite differences among calf plasma IgG concentrations, there was no effect of EHY or FREQ on colostrum yield, colostrum concentration of IgG or calf intake of colostrum. Similarly, apparent efficiency of IgG absorption and sera rotavirus neutralization titers among calves aged 14 d was not affected by treatment (P ≥ 0.36). Cow plasma IgG decreased (Quadratic = 0.02) as cows neared parturition and was not affected by EHY (P = 0.56) or FREQ (P = 0.14). We observed a quadratic increase in rotavirus neutralization titers in cow sera in response to vaccination, as expected. Sera rotavirus neutralization titers were not affected by EHY (P = 0.70) nor FREQ (P = 0.42). These data suggest that EHY but not FREQ may affect passive transfer of IgG.