Purpose This study tests the value of a measure of eating disorder (ED) psychopathology in predicting outcome following guided self-help in a non-underweight sample with regular binge eating. It examines whether early reductions in ED psychopathology are associated with remission status at post-treatment. Methods Seventy-two adults with bulimia nervosa, binge-eating disorder, or an atypical form of these illnesses received up to ten sessions of cognitive behaviour therapy-based guided self-help. Using a session-by-session measure of eating pathology and associated reliable change indices, response was analysed using receiver operating characteristic analysis to predict outcomes at post-treatment. Results In this routine care setting, nearly one-quarter of the sample achieved remission following GSH, approximately two-thirds of whom showed early change in ED psychopathology. Early change prior to session 6 was accurate in predicting later remission. Individuals showing early change did not differ from others on baseline characteristics or rates of attrition. Conclusion Data suggest that a majority of those who respond to treatment will do so before the second half of treatment, information that could be used to ensure that evidence-based treatments are used as effectively as possible. Level of evidence Level III.