This Medical Care Research and Review article examines associations among ambulatory surgery centers' (ASCs) organizational strategy, structure, and quality performance. Using 1997-2004 data from several large all-payer claims datasets, the authors operationalize quality performance as unplanned hospitalizations at 30 days after outpatient arthroscopy and colonoscopy procedures. Drawing on related organizational theory, behavior, and health services research literatures, the authors develop a conceptual framework, hypotheses, and fitted fixed and random effects Poisson regression models with the count of unplanned hospitalizations. Consistent with their hypotheses, the authors find that higher levels of specialization and the volume of procedures may be associated with a decrease in unplanned hospitalizations at ASCs.