Many patients report residual depressive symptoms despite seemingly successful treatment. With the investigators' previous funding, we developed - Mindful Mood Balance - an online treatment that targets RDS by teaching specific emotion regulation and depression self-management skills that are entirely compatible with antidepressant treatment. The investigators now propose a controlled study to determine whether MMB is more effective than usual care at reducing RDS and other key outcomes. If successful, MMB's online delivery format would provide high fidelity and low-cost empirically supported management of residual symptoms, leading to more robust remission, improved functioning and sustained recovery from MDD over time.