Objective: Outcome research has documented worsening among a minority of the patient population (5% to 10%). In this study, we conducted a meta-analytic and mega-analytic review of a psychotherapy quality assurance system intended to enhance outcomes in patients at risk of treatment failure. Method: Original data from six major studies conducted at a large university counseling center and a hospital outpatient setting (N = 6,151, mean age = 23.3 years, female = 63.2%, Caucasian = 85%) were reanalyzed to examine the effects of progress feedback on patient outcome. In this quality assurance system, the Outcome Questionnaire-45 was routinely administered to patients to monitor their therapeutic progress and was utilized as part of an early alert system to identify patients at risk of treatment failure. Patient progress feedback based on this alert system was provided to clinicians so that they could intervene before treatment failure occurred. Meta-analytic and mega-analytic approaches were applied in intent-to-treat and efficacy analyses of the effects of feedback interventions. Results: Three forms of feedback interventions--integral elements of this quality assurance system--were effective in enhancing treatment outcome, especially for signal alarm patients. Two of the three feedback interventions were also effective in preventing treatment failure (clinical support tools and the provision of patient progress feedback to therapists). Conclusions: The current state of evidence appears to support the efficacy and effectiveness of feedback interventions in enhancing treatment outcome. (Contains 10 footnotes and 6 tables.)