The article is devoted to the issue of the interaction of key institutions in the European Union in the process of adopting acts within the framework of the usual legislative procedure. The authors provide the analysis of the process of the ordinary legislative procedure on the basis of the norms of the primary and secondary law of the EU, as well as the decision making practice of the Parliament and the Council of the EU. It has been revealed that throughout the legislative procedure there is an active interaction of the Parliament, the Council and the EU Commission in order to develop and adopt the compromise text of an act. This interaction is most active in the form of informal trilateral consultations, the mechanism of which is not formally enshrined in the EU Constituent Treaties. A significant role in their implementation is assigned to the Commission, which in general, throughout the ordinary legislative procedure, acts as a kind of mediator in the interaction of the Parliament with the Council. In most cases the mechanism of tripartite consultations allows the adoption of a legislative act already in the first reading without the second and third readings. At the same time, the established practice of interinstitutional interaction within the framework of the usual legislative procedure increases the duration of consideration and adoption of draft acts.