Cap 2-5 cm broad, convex, expanding to nearly plane, sometimes slightly umbonate; margin incurved, becoming decurved, at maturity occasionally wavy to upturned; surface smooth, moist, hygrophanous, color varying from reddish-brown, ochraceous-brown to buff-brown, the margin lighter, in age fading to buff; flesh white, thin, unchanging; odor and taste mild.
Gills adnexed to notched, crowded, narrow, white to cream, unchanging.
Stipe 2-6.5 cm tall, 3-6 mm thick, cartilaginous, equal to enlarged at the base, hollow; surface smooth, colored like the cap, white mycelium at the base; veil absent.
Spores 5-7.5 x 3-4 µm, elliptical, smooth, non-amyloid; spore print white to pale cream.
Gregarious under oaks (Quercus); fruiting shortly after the fall rains.
Edible, but opinions vary on its culinary value; the stipes are tough and should be discarded.
This honey-brown to buff-brown, hygrophanous Gymnopus lives up to its species name, seldom venturing far from oaks. A close cousin, Rhodocollybia butyracea, is similarly colored, but has a lubricous cap, gills with finely scalloped edges, a cream spore print with a hint of pink, and a faintly striate stipe. It is more common under conifers but can occur in other habitats.