Technical Abstract: The ecological consequences of changes in environmental conditions associated with global climate change will depend in part on how organisms respond to those shifts at the individual level. Currently our understanding of genetic responses of plants to alterations in precipitation and temperature associated with climate change are based on model species in controlled greenhouse conditions. However, if we are to understand the mechanisms underlying species responses to climate change in natural systems, studies are needed that focus on responses of non-model species under field conditions. Thus, we measured transcriptional profiles of individuals of Andropogon gerardii, a C4 grass native to the tallgrass prairie ecosystem, in a field experiment in which both temperature and precipitation have been manipulated to simulate key aspects of forecasted climate change. By using microarrays developed for maize we were able to compare the relative influence of warming versus increased variation in precipitation on transcription level over 7,000 genes, identify responsive functional groups of genes, and correlate changes in gene transcription with physiological responses. Our results suggest that Andropogon gerardii is much more likely to shift transcription levels of genes in response to thermal stress than to water stress. Temperature-responsive genes included those associated with protein folding, antioxidant responses, and plant defense. Increased variation in water availability was associated with increased expression of genes involved in translation. We also identified candidate genes that demonstrated transcription levels closely associated with physiological variables, in particular chlorophyll fluorescence. These results indicate that an ecologically important species responds quite differently to different environmental shifts associated with global climate change and that these translational changes have the potential to influence phenotypic characters and ultimately adaptation.