Most research on parliamentary opposition focuses on constitutional and institutional aspects. This article argues that these approaches are limited in explaining differences between opposition parties. A case study of the Bavarian State Parliament, shows that there is support for the assumption that complex patterns of a number of factors, such as individual party groups’ ideology, history, their members’ socio-demographic background, and their informal rules of engagement, influence the way opposition parties behave. The study shows distinctive differences between the appearance and the strategies employed to influence the majority’s decision-making. The Social Democrats, a traditional mass party with over 40 years in opposition, focused on a strategy of professional, subject-oriented co-operation within parliament. The Greens chose confrontational power policies that had their main effect outside parliament. This stands in line with the party’s origin in grassroots movements and its culture of conflict resolution. Those findings raise the question of how party identities and policies coincide with the preference of one opposition strategy over another and they contribute to the discussion of how parliamentary behaviour and representative roles are interwoven
