Because of potential benefits on human health, the content of quercetin, the major flavonol found in onion (Allium cepa), could become a selection trait in breeding programs. Total flavonol concentration in onion was examined by spectrophotometric analysis at 374 nm in three long-day hybrid cultivars grown at three locations (Parma, Idaho; Grand Rapids, Mich; Elba, N.Y.), and in three shortday hybrid cultivars grown at one location in Georgia in three different fields. Mean total flavonol concentrations for long-day hybrids ranged from 176 to 232 mg·kg-1 (ppm) fresh weight and 110 to 173 mg·kg-1 fresh weight among short-day cultivars. No significant effect of location (state or field) was detected (P > 0.05). A significant (P > 0.05) cultivar by field interaction was detected in the short-day experiment, with the hybrid `Sweet Vidalia' showing significant differences among fields. Overall, our results suggest that quercetin content in onion, as expressed by the total flavonol content, does not vary depending on the growing origin, and therefore could be evaluated effectively in breeding or commercial material.