Plants annual. Culms 15-60 cm, ascending, glabrous. Sheaths shorter than the internodes, glabrous; ligules 0.5-1 mm, ciliate; blades 4-12 cm long, 1.5-6 mm wide, flat, spreading, evenly distributed, adaxial surfaces sparsely ciliate-pustulate. Panicles 6-22 cm long, (1)5-13 cm wide, open, sometimes contracted; branches terminating in a spikelet, lowest branches whorled, in verticels of 7-20; pedicels (2)3-6(8) mm, widely spreading, capillary. Spikelets 1.1-1.5 mm. Glumes thin, acute; lower glumes about 0.5 mm; upper glumes 1.1-1.5; lemmas 1.1-1.4 mm, acute; paleas 1-1.3 mm, hyaline. Fruits 0.6-0.9 mm, oblong, light brown; embryos 0.2-0.4 mm.
Sporobolus coahuilensis is primarily known from central Coahuila in Mexico. It has recently been found in Brewster and Hudspeth counties, Texas (Turner 2004). It is not clear whether it has been overlooked in the past or is a recent introduction. Sporobolus coahuilensis appears to be closely related to the widespread species S. pyramidatus, from which it differs in its long capillary pedicels and usually wider panicles.