Wyoming big sagebrush (Artemisia tridentata wyomingensis) treatments are often implemented to improve breeding habitat for greater sage-grouse (Centrocercus urophasianus), a species of considerable conservation concern. In 2008 and 2009, we measured vegetation structure available to sage-grouse for breeding at 19 sites that were prescribed burned during 1990–1999 and 2000–2006, 6 sites that were mowed during 2000–2006, and 25 paired, untreated reference sites in the Bighorn Basin of north-central Wyoming, USA. We compared minimum guidelines for canopy cover and height of Wyoming big sagebrush and perennial grass in arid greater sage-grouse breeding habitat (Connelly et al. 2000b) to measurements at our sampling sites. Sagebrush canopy cover and height at reference sites met the minimum guidelines. Sagebrush canopy cover at burned and mowed sites did not meet the minimum guideline, except for sites mowed on aridic soils measured during 2009. Burned and mowed (3 of 4 cases) sagebrush did not meet minimum height for breeding up to 19 yr and 9 yr post-treatment, respectively. Perennial grass canopy cover and height met the minimum guidelines for breeding habitat at reference, burned, and mowed sites. Burning increased grass canopy cover, but not height, compared to reference sites in 2 of 8 instances. Because burning, but not mowing, infrequently enhanced grass cover, but not height, and sagebrush structure was reduced by both practices for long periods, managers should consider how treatments may negatively affect Wyoming big sagebrush communities for sage-grouse and consider other practices, including continued nontreatment and improved livestock grazing, to increase grass cover and height. © 2012 The Wildlife Society.