The purposes of this study were to develop a multivariate statistical model related to plant succession, to classify by seral stage, and to monitor succession in Wyoming big sagebrush shrubsteppe habitat (Artemisia tridentata ssp. wyomingensis/Agropyron smithii–Bouteloua gracilis) in Thunder Basin National Grassland, Wyoming. This model can be used by range and wildlife managers to evaluate management alternatives by assessing changes in plant species cover and composition within and between seral stages. Four ecological seral stages that represent early to late succession were quantitatively identified with an estimated 92% accuracy. Three key plant species provided the necessary information to define seral stages and monitor trends. Percent canopy cover and percent frequency (used to calculate index values: % canopy cover ×% frequency of occurrence) of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), western wheatgrass (Agropyron smithii), and blue grama (Bouteloua gracilis) are the only field measurements required for this model.