Considering the growing contestation of expertise in the public sphere, this chapter explores the institutionalisation of expert groups and how the European Commission (EC) has adapted its use of expertise. Drawing on established conceptualisations about the functions of expertise during the policy-making process, our analysis is two-fold. Firstly, we consider macro level changes and broader trends in the entire Expert Groups (EGs) system. Secondly, we examine the micro level changes of expert advice use in two case studies. Based on new data from the Commission’s register of EGs, as well as on interviews, primary and secondary sources, we find improvements with regard to transparency, conceptualised as improved access to the register. The EC has also specified better the classification of different types of experts. Furthermore, the two case studies of EGs—focusing on financial sustainability and lowering limits of industrial pollution—show that the use of expertise is both instrumental and strategic. Concretely, the strategic (consensus-building) use of expertise helped to narrow down the range of viewpoints. Eventually, this facilitated the identification of compromises and acceptable policy solutions in the policy shaping stage of the EU legislative process.