Floristic quality assessments (FQA) are widely used to assess ecological condition, based on plant species' coefficients of conservatism, or C values, but these values are typically assigned at the state level, limiting their regional consistency. We developed ecoregional C values (eC) using standard expert-based team review, partly informed by preexisting state C values for the 5 EPA ecoregions that cover New England and part of New York. We evaluated a total of 3686 taxa, with separate eC values for each ecoregion in which they occurred. We compared the performance of the C and eC values using the response of FQA metrics (mean C, cover-weighted mean C) to a disturbance gradient, based on readily available datasets in Maine and Vermont. The eC values typically performed moderately better than state values and provide a region-wide tool for assessment methods. All eC values are available on the Universal FQA website.