Collybia dryophila

Common Name: Oak-loving Collybia
Description: Cap 2.5-5cm across, convex and then flat, margin inrolled; ochre-brown to reddish or pale tan; smooth, dry. Stem 10-70 by 1.5-5mm high and wide.
Habitat: usually gregarious, under both oak and pine. Rather common. Found in most of North America.
Edible: yes, but not worthwhile.

Source: Mushrooms of North America by Roger Phillips.