Eragrostis fosbergii is a perennial grass in the Poaceae family with stout, tufted culms (stems) 60 to 100 cm (24 to 40 in) long, which arise from an abruptly bent woody base. The leathery leaf blades, 40 to 60 cm (16 to 24 in) long and 5 to 10 mm (0.2 to 0.4 in) wide, are flat but curl inward towards the apex. The small flowers occur in complex clusters that are somewhat open, pyramidal, and 20 to 40 cm (8 to 16 in) long. The pale to dark green spikelets (ultimate flower clusters) generally contain three to five flowers and are about 5 mm (0.2 in) long. The slender glumes (small bracts at the base of the spikelet) have margins fringed with long hairs. The lemmas (inner bracts that subtend the flowers) have loosely overlapping margins, which are occasionally fringed with hairs. The fruit is a grain.