Practitioners are being placed under increasing pressure to evaluate the success of their outreach activities, both by government and by their own universities. Based in a reductionist doctrine of "evidence-based practice", there is a desire to demonstrate the effectiveness and value-for-money across activities that now account for around £175 million per year across England. This article examines some of the difficulties in evaluating the complex social world of outreach and suggests a "small steps" approach to overcome some of these. This uses the idea of a transformative "theory of change" as a framework for understanding the particular contribution made by discrete activities within a wider portfolio, providing a more reliable form of inference than attempts to "prove" impact over longer timeframes.