This article aims to explain longitudinal and cross-sectional variation in regional government composition – oversized majorities and incongruence between regional and national governments (cross-cutting) – and regional government alternation. The analysis focuses on the explanatory value of a wide range of regional-level institutional variables, such as majoritarian vs. proportional voting systems and established practices of consociationalism. In addition, it provides a tentative exploration of the impact of regional (i.e. non-state-wide) parties on government composition and alternation. The findings show that most institutional variables have the expected impact, e.g., majoritarian voting systems increase government alternation and cons...