Renewable energy cooperatives envision and manifest an alternative way of organising within the energy system (and beyond). Yet, despite their growth, it is uncertain whether such initiatives are able to increase and deepen their impact, leading the transition to an environmentally sustainable and socially just energy system. This paper presents insights from a strategic dialogue co-organised with the Dutch national interest group of renewable energy cooperatives "ODE Decentraal". We used transition management as action research methodology to organise the dialogue to understand and support the transformative potential of the cooperative energy movement. The dialogue helped to clarify the challenges and possibilities for scaling energy cooperatives beyond the niche, supporting at the same time the participants to reflect, strategize and develop a shared transition agenda. This contribution presents and analyses our intervention and its impact, also specifically evaluating the potential of transition management to facilitate social learning processes, reflexivity and the development of strategic actions. Our intervention confirmed the hypothesis that actors in the niche often focus too much on the competition with the regime for individual goals, thereby failing to collectively strategize and engage with incumbent regimes in a systematic way.