Cap 3-6 cm broad, convex, sometimes with a low umbo expanding to nearly plane at maturity, the disc then sometimes slightly depressed; margin entire to wavy, decurved, becoming more or less plane to slightly upturned; surface glabrous, lubricous, dark reddish-brown, the margin pallid, fading overall in age; odor and taste mild.
Gills adnate, white, close to crowded, moderately broad, the edges finely toothed.
Stipe with thickened strands of white mycelium; surface striate, tan-buff to pinkish-buff, paler at the apex; veil absent.
Spores 3.5-5 x 3.5-4.75 µm, nearly globose, smooth, nonamyloid; spore print off-white.
Scattered to gregarious on needle duff or on rotting wood in conifer woods; fruiting late fall to mid-season.
This attractive Rhodocollybia is characterized by a deep reddish-brown, lubricous cap, white, finely scalloped-edged gills, and a buff-brown to pinkish-brown, striate stipe. Rhodocollybia butyracea is similar but usually paler. A microscope is required to confirm an identification. The spores of Rhodocollybia badiialba are nearly round, while those of R. butyracea are elliptical and larger.