Expanding on Porter (2013), this chapter outlines the contributions that external oversight agencies can, and do, bring to police reform, with a focus on proactive activities. This chapter discusses how a problem-oriented approach can help to frame these efforts and promote the value of collaborative partnerships between oversight and police agencies to improve policing services to the community. The challenges of collaborations are discussed, but several case study examples present evidence that productive relationships have led to improvements in policing, at least at the jurisdictional level.