Why do opposition parties support legislation?

A government in control of a parliamentary majority does not require opposition parties’ support to pass laws. Yet such support happens. In six recent legislative periods two thirds of the bills enacted by the Austrian parliament was supported by at least one opposition party. The paper presents the outlines of a theory of parliamentary consensus seeking between government and opposition parties that draws on theories of issue competition and derives specific hypotheses on the conditions that make opposition support more or less likely. It tests the relevance of party-related factors (such as party policy salience and position), government type, characteristics of the legislative proposal (e.g. importance of bill), party interaction in the legislative process, as well as timing in the electoral cycle while keeping institutional factors constant.