This article presents the key findings on participant development in Codevelopment Action Learning (CAL) groups from the second phase of Codev-Action, a Canadian action research partnership. The study used a mixed-methods design to quantitatively measure CAL's contribution to work self-efficacy development in 154 participants from 50 CAL groups over a roughly one-year period. The study also used cross-sectional Qualitative Comparative Analysis (QCA) approach to identify which facilitation behaviour configurations were most likely to increase work self-efficacy among the participants who brought a topic to their group (n = 92). Quantitative results show a significant improvement in work self-efficacy, including perceived effectiveness with regard to teamwork, problem solving, and work politics. Qualitative analysis shows a set of five configurations involving 10 facilitation behaviours that, when used in CAL groups, can support increased work self-efficacy. These results provide empirical evidence for CAL's contribution to the development of work self-efficacy. Given the well-known impact of self-efficacy on task performance, the progress made in CAL sessions is a significant asset for decision makers.