Data suggest that obsessive-compulsive (OC) symptoms are commonly observed in adolescents with eating disorders and predict poorer treatment response. Further, emerging data among adults suggest that changes in OC symptoms relate to changes in eating disorder symptoms across treatment. Given evidence that early invention decreases risk for protracted illness, evaluating processes that may relate to treatment response will be useful in increasing the effectiveness of existing interventions. Therefore, the current investigation explored changes in general and eating disorder-specific OC symptoms throughout family-based treatment (FBT) and cognitive behavioral therapy (CBT) for bulimia nervosa (BN), as well as associations among these changes and eating disorder outcomes at follow-up.