Cap 7-20 cm broad, convex with incurved margin, nearly plane in age; surface dry, yellowish-orange to orange with fine brown scales; flesh thick, yellow, turning red in KOH; odor mild to pungent, taste bitter.
Gills close, adnate, notched, to slightly decurrent; yellow, becoming orange.
Stipe 7-21 cm long, 1-4 cm thick, yellow-orange, lighter than the cap, streaked with brown fibrils, equal, club-shaped, or ventricose, usually narrowed at the base; partial veil membranous, yellowish, forming a usually persistent superior ring.
Spores 7.5-10 x 4.5-6 µm, roughened, elliptical. Spore print rusty-orange.
Fruiting from early fall to mid-winter in clusters on stumps and logs of both hardwoods and conifers.
Inedible, very bitter.
Gymnopilus spectabilis is well named as its yellowish-orange clustered fruitings are often massive with dinner plate-sized mushroom caps. The combination of a clustered habit on wood, orange cap, well developed ring, bitter taste and rusty spores make it easy to identify.
Gymnopilus ventricosus may also occur locally, but the material we have studied generally appears closer to Gymnopilus spectabilis.