The capability of organizations to respond to unexpected events has been investigated from different theoretical angles: organizational learning, improvisation, ambidexterity, resilience, to name but a few. These concepts, however, hardly ever refer to structural characteristics. Against this backdrop, the aim of this paper is twofold. First, based on systems and organizational learning theory, it will theoretically link the characteristics of organizational structure with organizational responses to unexpected external jolts, thus contributing to better understand the reactions of organizations to the unexpected. Second, it will empirically illustrate the relation of organizational structure with organizational responses by investigating how Civil Society Organizations (CSOs) in Austria reacted to the unexpected inflow of refugees from Central Europe. In 2015, CSOs accepted a wide range of responsibilities and worked together with government entities to provide shelter, catering, and transport for almost one million refugees. Based on participant observations during operation, in-depth interviews (2015 and 2016) and focus groups with decision-makers (2017), we will sketch three longitudinal case studies of organizations with very different structures, concentrating on the processes and operations they developed during the crisis. Our findings show that their responses are closely related to their structure, specifically to the flexibility and the stability of structural elements. Remarkable changes took place in all organizations investigated. Initial responses and first structural changes occurred mainly where the structure already allowed for flexibility. Yet in the long run, the adaptations also impacted the stable structural elements.