Forage consumption of free-ranging beef cows for breeds differing in milk production potential was estimated in the summers of 1983 and 1984. Hereford (HH) and 75% Simmental-25% Hereford (3S1H) breed groups were used in 1983. In 1984, 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (SH), and 50% Angus-50% Hereford (AH) breed groups were added. Six mature (6-or 7-yr-old) lactating cows of these breed groups were used each year. Fecal output was estimated during June, July and August each year using the chromic oxide dilution technique. A correction factor was derived by comparing estimated fecal output values to actual measurements using fecal bags. Monthly forage extrusa collections for in vitro organic matter disappearance determinations were obtained using esophageal-cannulated cows. Breed groups did not differ in body weight (P>.10) in either year and averaged 549kg. No significant difference in average mean intake expressed as a percentage of body weight per day (%BW/d) was found between the breeds in 1983. In 1984, important breed group differences were detected (P<.O1). Average mean intakes for 1S3H, HH, AH, SH and 3S1H were 2.2, 2.3, 2.5, 2.6 and 2.8% Bw/d, respectively. These results provide an initial basis for evaluation of cow types of differing production potential that are foraging in a restrictive rangeland environment.