This dissertation compares the contentious responses to austerity in Portugal and Spain in the context of the Eurozone crisis and the Great Recession between 2008 and 2015. Despite many similarities in the origins and socio-economic effects of the crisis, the dynamics of contention in each country differed in terms of number, rhythm and actors. While Portugal and Spain experienced parallel protest dynamics until 2011, after that point the former falls into a pattern of “stop-and-go” with sporadic large events by social movements. In contrast, in Spain mobilisation and confrontation levels rose into a sustained wave that lasted until late 2013 and leading to the emergence of new political parties. The dissertation aims at explaining these different trajectories and outcomes arguing that they are connected to the nature and configurations of the actors in the process, which come to shape the kinds and forms of claim-making involved. Rather than focusing solely on social movements, the dissertation looks at a plurality of actors and claims. Following a cycle-based approach, the focus of the analysis falls on the relations between institutional and non-institutional actors in reshaping the political sphere in each country. The research design is based on process tracing and paired comparison, combining a protest event analysis with interviews. Analytically, I consider the following dimensions: time and space, actors, networks and alliances; organization, repertoires and strategies; claims and frameworks. The empirical chapters reveal contrasting dynamics at work in each country. In Portugal, even if social movements emerged, austerity was mainly challenged within the borders of the existing institutional framework, both through the control of protest movements by parties and trade unions and through an internal recomposition of the left leading to a new system of alliances. Rather than a disruptive discourse, the dominant actors wanted to conserve the status-quo of the welfare state in Portugal against austerity. In Spain, social movements developed as a disruptive force that questioned both austerity and political institutions. Relatively stronger and autonomous than in Portugal, the Spanish movements were able to collaborate on a more equal footing with institutional actors, constituting overlapping protest dynamics that sustained mobilisation. In contrast to Portugal, this resulted in a variety of discourses and conceptions of citizenship expressing the different interests in the field. This dissertation shows that cycles of contention are shaped by the way the contentious field is organized and that the types of relations between institutional and non-institutional actors play a fundamental role in the way such cycles unfold.