The objective of this study was to evaluate the inclusion rate of pea hay in diets for beef cattle based on barley or oat hay. Six ruminally-cannulated heifers (407 ± 38 kg) were used in a 6 × 6 Latin square (25-d periods) with a 2 × 3 factorial design. Treatments included whole-crop barley or oat hay with pea hay blended in to achieve inclusion rates of 0, 15, or 30% (DM basis) of the forage. Pea hay inclusion increased dry matter intake (DMI; P = 0.03) by 0.75 kg/d relative to diets without pea hay, but the response was not linear or quadratic. Inclusion of pea hay linearly increased mean ruminal pH (P = 0.039), the concentration of butyrate in ruminal fluid (P = 0.013), plasma urea-N concentration (P = 0.001), and quadratically increased ruminal ammonia concentration (P < 0.001). Pea hay inclusion reduced CP digestibility by 2.87% relative to cereal-only treatments (P = 0.025), but did not affect N intake, microbial N, or N excretion. Overall, pea hay inclusion increased DMI, increased ruminal butyrate concentration, but reduced CP digestibility without affecting N balance.