Objective We addressed two questions regarding health system consolidation through the acquisition of ambulatory clinics: (1) Was increasing health system size associated with improved diabetes care performance and (2) Did the diabetes care performance of acquired clinics improve postacquisition? Data Sources/Study Setting Six hundred sixty‐one ambulatory clinics in Minnesota and bordering states that reported performance data from 2007 to 2013. Study Design We employed fixed effects regression to determine if increased health system size and being acquired improved clinics' performance. Using our regression results, we estimated the average effect of consolidation on the performance of clinics that were acquired during our study. Data Collection/Extraction Methods Publicly reported performance data obtained from Minnesota Community Measurement. Principal Findings Acquired clinics experienced performance improvements starting in their third year postacquisition. By their fifth year postacquisition, acquired clinics had 3.6 percentage points (95 percent confidence interval: 2.0, 5.1) higher performance than if they had never been acquired. Increasing health system size was associated with slight performance improvements at the end of the study. Conclusions Health systems modestly improved the diabetes care performance of their acquired clinics; however, we found little evidence that systems experienced large, system‐wide performance gains by increasing their size.