Iwaasa, A. D., Jefferson, P. G. and Birkedal, E. J. 2014. Beef cattle grazing behaviour differs among diploid and tetraploid crested wheatgrasses (Agropyron cristatum and A. desertorum). Can. J. Plant Sci. 94: 851-855. A study was conducted over 4 yr (1999, 2000, 2002 and 2003) at Swift Current to evaluate the forage preferences of steers grazing five different crested wheatgrass (CWG) cultivars: Kirk (2n=28), Fairway (2n=14) and Parkway (2n=14) [Agropyron cristatum (L.) Gaertn.], Hycrest (2n=28) (A. cristatum×A. desertorum) and Nordan (2n=28) [(A. desertorum (Fisch. Ex Link) Schult.)]. Animal grazing frequencies for each CWG cultivar patch were converted to percentages (Grazing%) for each grazing time period. Grazing% for Kirk and Hycrest CWGs were similar with Nordan having higher (P<0.05) Grazing% compared with the hybrid and diploid CWGs. Contrasts revealed no differences (P=0.48) in Grazing% between diploid versus hybrid cultivars, while higher (P<0.01) Grazing% were observed for tetraploid compared with diploid and hybrid CWG cultivars. For forage nutritive values, significant Cultivar (P<0.01) and Year (P<0.0001) main effects were observed. Overall mean values for percent crude protein (%CP) and percent acid detergent fibre (�F) for Nordan, Kirk, Hycrest, Fairway and Parkway were 10.6±0.3 and 29.2±0.4, 11.0±0.3 and 28.7±0.4, 10.4±0.3 and 29.7±0.4, 9.9±0.3 and 28.5±0.4, and 10.0±0.3 and 28.7±0.4, respectively (± SE). Correlation coefficients between Grazing% and all nutritive value constituents were low and not significant. This study observed grazing preference differences among different CWG cultivars that may lead to grazing management strategies to improve pasture utilization potential and animal production.