The European Parliament was from the start viewed and treated as the Weaker part in the EU in comparison to the Council and the Commission. But the power and influence of the European Parliament has been rising step by step to the position it holds today. This study puts the searchlights on the organisation and organisational changes that has happened to the staff in the European Parliament during the last three treaties. It focuses especially on the changes regarding the staff that provides assistance to the MEPs, and in that sense are connected to the treatment of the political decision-making. The previous research in this area are not extensive, but the results has pointed in the direction of that the staff plays an important role in supporting the MEPs and helping them to handle the informational deficit that they might face when making policy choices. The staffs role in supporting the parliaments position in relation to its executive has also been lifted. The aim of this study to investigate changes in the structure of the administrative support in the European Parliament, and also look at the explanations for these changes; what caused the changes to happen and why the EP-administration was designed in the way it is. By using the same analytical framework as is used for government administrations in nation states I argue that we can see interesting patterns that help us understand more about these questions. The explanatory factors have been drawn from two core theoretical perspectives on organisations, the instrumental and the institutional perspective. I have used process tracing as method to look at two main reform processes and the snowball method has been used to find the investigated documents. The main conclusions is that there has been both intentional changes and changes that comes as consequences of decisions that are not entirely up to the parliament itself. As regards the assistance to MEPs the organisation of the administration has changed significantly towards providing faster and more qualified support to ensure the quality of the legislature and meet the needs of the MEPs. The reform processes has been characterised by that the parliament is a strongly institutionalised organisation and by negotiations between the relevant stakeholders, rather than a rational design approach. The proposals put forward in the reform process was motivated from dissatisfaction amongst the MEPs, and also from that the parliament needed to adapt to a new situation with greater powers and an enlarged EU. The negotiations, as well as political compromises, have restrained a rational design of the Parliament.