Technical Abstract: Little bluestem (Schizachyrium scoparium, SCSC) and big bluestem (Andropogon gerardii, ANGE) are among the dominant species of tallgrass prairie in central Oklahoma. Little bluestem is considered less valuable for grazing due to its tussock growth form and perceived lower forage quality. Productivity and quality of both species change during the growing season, altering their forage value. This study tested whether forage production and quality of these grasses differed during the growing season. Data were collected during April through September (12 dates) 2000 from a tallgrass prairie site (16 plots) in central Oklahoma. Aboveground production (AGP) and its composition were defined on 0.5 m2 quadrants, and tiller growth stage of both species was determined. Collected tillers were processed and scanned by near infrared reflectance spectroscopy to predict nitrogen content, in vitro dry matter disappearance (IVDMD) and neutral detergent fiber (NDF). Data were analyzed as repeated measures for date (repeated element) and species effects. AGP displayed a non-linear increase during the growing season with ANGE, and SCSC producing 34 (+/- 6) % and 16 ( +/- 4) % of total AGP, respectively. Changes in growth stage of the two species differed (P<0.05) and were non-linear, with SCSC being more mature. Change (decline) in N content over dates was significant and non-linear, but species were not different. Significant species x date interactions were noted for IVDMD and NDF; SCSC had lower IVDMD and higher NDF. Results suggest little bluestem can supply modest amounts of N to grazing animals during parts of the growing season, if pastures are managed to provide access to current growth.