Fire is natural in sagebrush (Artemisia L.) communities. In this study, we quantify effects of time since last burn (TSLB) on shrub cover over a 70-year (yr) fire chronosequence. We sampled mountain big sagebrush communities with very large-scale aerial (VLSA) imagery and measured sagebrush, antelope bitterbrush (Purshia tridentata [Pursh] DC.), and spineless horsebrush (Tetradymia canescens DC.) cover. We used segmented regression to describe two cover phases with respect to TSLB. Phase 1 was when cover responded to TSLB and Phase 2 was when cover had reached a steady state with respect to TSLB meaning that expected shrub cover did not change with increasing TSLB. In the first year after burning, total shrub cover was 5%. In Phase 1, total shrub, sagebrush, and bitterbrush cover increased with TSLB. Bitterbrush transitioned to Phase 2 in 6 yr, but 19 and 18 yr, respectively, were needed for sagebrush and total shrub to transition. Horsebrush cover decreased with TSLB from 2.1% to 0.2% over 27 yr. Steady-state cover for sagebrush, bitterbrush, and total shrub were 30.6, 2.8, and 39.8%, respectively. These data describe postfire shrub cover change in mountain big sagebrush communities that can be used in management plans that meet shrub cover objectives.