Plants 6-30 cm. Stems glabrous or scabrous. Leaf blades linear to linear-oblanceolate, (5-)10-80(-95) × 0.7-2.6(-3) mm, cauline bases not auriculate or clasping, distalmost cauline abruptly reduced. Heads not immediately subtended by leaflike bracts. Involucres 7-11.5(-13) mm. Phyllary apices abruptly acute to obtuse, apiculate to cuspidate. Ray florets 0. Disc florets 7-28. Cypselae 5-6 mm, faces glabrous or sparsely scabrous. 2n = 20. Flowering Jul-Sep. Barrens, limestone and clay outcrops and ridges, sandy or gravelly slopes, shaley slopes (often with Frasera coloradensis), cactus-scrub, dry powdery clay, gypsiferous shale, ditches, pastures, fencelines, drying shorelines, usually in sites within shortgrass prairie; 1200-1900 m; Colo., Kans. Oönopsis engelmannii grows in Baca, Bent, Cheyenne, Denver, El Paso, Elbert, Kiowa, and Lincoln counties in Colorado, and in Hamilton County, Kansas. Hybrids are documented between O. engelmannii and O. foliosa var. foliosa.