Does the organization of the assembly affect whether governments deliver policy that reflects the public’s changingpreferences? Cross-national analyses of public opinion and policy outputs for policies concerning welfare and immigrationshow that governments respond to shifts in public opinion in systems with a dominant chamber but not where bicameralismis strong. Our theory’s emphasis on the distribution of powerbetweenchambers further explains differenceswithinbicam-eral systems: constraints on policy change mean that responsiveness is weaker where power is equally distributed betweenchambers but more robust where power is concentrated in the lower house. Evidence from institutional change in Belgium,where the fourth state reform shifted power away from the senate and disproportionately toward the lower house, providescorroborating evidence that policy becomes more responsive when constitutions concentrate legislative power. This study’sfindings have implications for our understanding of how bicameralism matters for government responsiveness to publicopinion.