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Grazing of native range in the same season occurs due to logistics and convenience of livestock management.    Records of 100 pastures used by beef cattle has been recorded since 1991 at the 22,257 ha USDA-ARS Fort Keogh LARRL Miles City, MT, where native vegetation is predominately western wheatgrass (Pascopyron smithii), needle and thread (Heterostipa comata), and blue grama (Bouteloua gracillis) grasses normally receiving 350 mm precipitation annually.  We sampled canopy and basal cover in pastures that were grazed over 60% and less than 20% of the time in spring (April-June), summer (July-October), and winter (November-March) and those without a dominant season of use (SOU) in loamy and clayey ecological sites (ES).  Three 50 m transects were sampled for basal and canopy cover at 3 sites in each pasture for each SOU and ES. ES, SOU, percentage use (%U)(H from 62-77%, L from 9-17%, NONE for sites without a dominant SOU) and their interactions were evaluated and analyzed using Proc Mixed (SAS 2009) as a 2 x 3 × 3 factorial arrangement of treatments.  Percent bare ground (P<0.05) was greater on clayey (56±2.9%) than loamy ES (46±2.9%).  SOU x %U interacted (P<0.05) to influence percent of bare ground in pastures grazed primarily in summer having the lowest amount of bare ground cover (32±6%).  Litter cover was affected by ES*SOU, ES*%U and SOU* %U interactions (P<0.05).  Cool season grass cover was highest (P <0.05) in pastures grazed primarily in winter (79±3.7%) and lowest (P<0.05) in pastures grazed primarily in spring (32±3.7%).  An ES*SOU*%U interaction (P<0.05) altered warm season grass cover.  Annual grass cover was impacted (P<0.05) by an ES*%U interaction.  Annual grass cover was highest (P<0.05) on clayey ES without a dominant SOU (25±2%). Intentional recurrent SOU can change proportions of bare ground, litter, and species composition in northern mixed grass prairie.