This article uses a case study of the Human Fertilisation and Embryology Act 2008 to examine the legislative role of the UK Parliament. Parliament is often considered to be a weak legislative actor, although this view has increasingly been challenged by legislative scholars. In this case, Parliament exercised agenda-setting powers at the pre-legislative stage that produced a significant impact on legislative outcomes. The article demonstrates the value for legislative studies of disaggregating the legislative timeframe and thereby examining the power of legislatures beyond the formal decision-making process. It also identifies a set of enabling conditions – for example, extended pre-legislative scrutiny, low political salience, and synchronisation of committee timelines with the legislative process – under which legislatures might exercise agenda-setting power in other areas of policy. The case study finds that those parliamentarians who engaged with policy in the agenda-setting phase exerted greater influence over policy outcomes than those who engaged at the decision-making stage.