Since May 15, 2011, when demonstrators decided to camp at the Puerta del Sol, Madrid’s public plazas have lived with the rhythm of popular assemblies organized by the indignados (the outraged). Based on ethnographic research carried out for nine months in the Spanish capital on roughly sixty assemblies observed, this article shows how participants interact in these meetings and make decisions by using consensus rule. It analyzes the implementation of deliberative practices within a social movement and scrutinizes their routinization as mobilization becomes institutionalized.