Health care quality measurement initiatives often use health plans as the unit of analysis, but plans often contract with provider organizations that are managed independently. There is interest in understanding whether there is substantial variability in quality among such units. We evaluated the extent to which scores on the Consumer Assessment of Health Plans Study (CAHPS) survey vary across: health plans, regional service organizations (RSOs) (similar to independent practice associations [IPAs] and physician/hospital organizations [PHOs]), medical groups, and practice sites. There was significant variation among RSOs, groups and sites, with practice sites explaining the greatest share of variation for most measures.