The type specimen was collected from Horse Heaven Hills in Benton County, Washington.

Here it was found growing on soil in a bunchgrass (bluebunch wheatgrass, Pseudoroegneria spicata) steppe.

Soredia are usually present on the thallus surface; they are dark gray to greenish-black to black, organized into regions of rounded soralia.

[1] Although morphologically similar to Trapeliopsis californica, T. steppica can be distinguished from that species by the presence of soralia that is dark and rounded, and a thinner upper cortex.

[1] In addition to Washington, Trapeliopsis steppica has also been recorded from eastern Idaho south to southern California, in grassland and in shrub–steppe.