In parliamentary systems, the need to preserve the political agreement that sustains the executive often motivates legislative involvement in policymaking. Institutional arrangements regulating executive–legislative relations and ministerial autonomy also structure parliamentary participation. However, empirical evidence of these effects remains limited to a few policies and countries. European Union legislation provides the opportunity to test expectations about legislative involvement for different types of measure across various institutional arrangements, across multiple policy areas, and across time. In this article, we investigate legislative involvement in the transposition of 724 directives in 15 member states from 1978 to 2004. Our results confirm that involvement increases as conflict between the responsible minister and her coalition partners intensifies. The discretionary scope embedded in the directive further inflates this effect. Additionally, parliamentary involvement decreases as the government’s institutional advantage over the legislature increases, especially if intracoalitional conflict deepens.