The objective of this study is to perform a randomized clinical trial (ACHIEVE) to definitively test the efficacy of an innovative, practical intervention to accomplish weight loss in overweight and obese persons with SMI. This multi-site trial will enroll consumers with SMI who attend ten psychiatric rehabilitation centers in Maryland and randomize participants to the ACHIEVE intervention or control. Intervention participants will receive group and individual weight loss counseling sessions and group physical activity classes. Co-primary outcomes will be change in weight from baseline to 6 and 18 months.