Traditional theories of collective action would predict that, after a triggering event, the trajectory of a wave of protest is determined by the institutionalisation–radicalisation tandem. Based on the Spanish cycle of anti-austerity and against the political status quo protest in the shadow of the Great Recession, this article contends with this approach, as a clear trend towards radicalisation is never observed as the cycle unfolds. An alternative interpretative framework is developed to understand protest trajectories when collaborative inter-organisational strategies prevail. The eventful 15M campaign triggered in 2011 represents the most remarkable turning point in the Spanish socio-political mobilisation scene in recent years and had a transformative capacity over subsequent protest endeavours. Specifically, after the 15M campaign, the combination of downward scale shift and coalition building shaped the trajectory of mobilisation, and allowed for the peak of protest to persist until late 2013, when institutionalisation took over. Data from an original Protest Event Analysis dataset are used to illustrate the main arguments.