Changes in land management and climate alter vegetation dynamics, but the determinants of vegetation changes often remain elusive, especially in global drylands. Here, we assess the determinants of grassland greenness on the Mongolian Plateau, one of the world’s largest grassland biomes, covering the province of Inner Mongolia in China and Mongolia. We use spatial panel regressions to quantify the influence of precipitation, temperature, radiation, and the intensity of livestock grazing on the normalized difference vegetation indices (NDVI) from 1982 to 2015 at the county level. The results suggest that the Mongolian Plateau experienced vegetation greening during the growing season from 1982 to 2015. Precipitation and animal density were the most influential factors contributing to higher grassland NDVI values for Inner Mongolia and Mongolia. Our results highlight the dominant effect of climate variability, especially that of precipitation, on the grassland greenness in Mongolian drylands and challenge the common belief that higher grazing pressure is principally associated with land degradation. The analysis exemplifies how representative wall-to-wall results can be attained from examining space?time data via recently developed software options. This article is protected by copyright. All rights reserved.