We investigated the spatial and temporal variability of herbaceous radiation use efficiency (RUEh) and herbaceous aboveground net primary production (ANPPh) of big sagebrush ecosystems in Wyoming’s Upper Green River Basin. Using a combination of field data, Sentinel-2 satellite imagery, and global radiation datasets, we inverted the Monteith model to estimate RUEh across 80 field plots. We examined the influence of environmental factors such as temperature, precipitation, soil texture, and grazing intensity on RUEh and ANPPh. Our findings revealed significant variability in RUEh, with a mean of 0.56 g/Mj, and ANPPh, averaging 32 g/m2/year. RUEh was significantly influenced by growing season evapotranspiration, while ANPPh was primarily driven by annual precipitation and soil clay content. Additionally, we explored the regional and interannual variation in ANPPh over 1075 sites using 5-day averages over 5 years. ANPPh peaked in late June to early July, closely following the peak of photosynthetically active radiation (fAPARh), while maximum temperatures peaked later in summer. Precipitation emerged as a major factor explaining 54% of the spatial variability in ANPPh across the study region.