Inadequate seed supplies of adapted blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] and little bluestem [Schizachyrium scoparium (Michx.) Nash.] cultivars limits the use of these two species in the northern Great Plains of Western Canada. This study examined variation in seed yield traits of 11 blue grama and 14 little bluestem plant collections obtained from southern Manitoba, Canada to facilitate development of improved germplasm of these species. Measurements of seed yield traits including harvested air‐dried biomass, culm number, seedhead number, seed yield, caryopsis weight, and kernel index were taken from randomized complete block spaced‐plant nurseries. Tests were conducted for 2 yr at Winnipeg and 1 yr at Carman, MB, Canada. Collections within both species differed significantly for all traits. Significant collection × year (Winnipeg) and collection × location interactions were present for biomass and seed yield, and many of the seed yield‐component traits. While significant, the interactions resulted in few changes in rank among collections. Generally, the most northern collection in both species showed earlier anthesis, produced less biomass, and had lower seed yield than more southern collections. These findings indicate that indigenous plant collections of blue grama and little bluestem show high levels of genetic diversity for biomass, seed yield, and seed yield components, which provide opportunity for development of adapted cultivars with enhanced forage and seed production capability for the region.