Flowering stem 20–40 cm tall. Leaf-blade to 15 cm long, 2–4 mm diam. at base, green, apex lax, often withered at flowering. Flowers 10–25, fragrant, green to reddish brown, subsessile in a sparse to moderately dense spike 6–12 cm long; ovary obovoid, 4–5 mm long, green; sepals 7–8 mm long, dorsal sepal ovate-lanceolate, forward pointed, lateral sepals free, linear-lanceolate, nearly parallel, erect to recurved; petals 6–7 mm long, linear to linear-obovate, incurved, blunt. Labellum ovate, 5–6 mm long, white or pinkish, recurved at right angles near the middle, margins crinkled; apex triangular, subacute; callus plate much-raised, broad, extending almost to labellum apex. Column appendages ovate-elliptic, c. 2 mm long, obtuse. Flowers Sep.–Oct.
Similar in appearance to Prasophyllum frenchii, but generally less robust with more widely opening flowers and different structure of the labellum callus.
Prasophyllum fosteri has become critically endangered due to substantial loss of habitat.
