Self-sustaining trout populations in mountain streams depend on the presence of suitable spawning habitat. However, current watershed-scale habitat inventory techniques do not assess trout spawning habitat. A spawning substrate evaluation technique is a logical component of such inventories because it would provide data on spatial patterns of suitable substrate across watersheds. We evaluated a visual technique designed to assess substrate suitability for trout spawning. Comparisons of visual assessments of potential spawning sites to those using a single-probe freeze-core were made. The visual method of evaluating spawning substrate was nearly as good as the freeze-core method. Considering the time, labor, and cost efficiency of visual substrate assessment, this visual technique is a reasonable alternative when evaluating trout spawning substrate at the watershed scale.