Plenary meetings of the COSAC are held twice a year, one during each six-month presidency of the Council of the European Union in the Member State holding the presidency. In the plenary meetings of the COSAC, the committees for Union affairs of Member States' national parliaments are represented by a maximum of six members and the European Parliament by six members. Three members of the parliaments of each candidate country are invited to participate in the plenary meetings as observers.
The plenary meetings of the COSAC provide a platform for exchanging information and best practices between Parliaments of the European Union, in particular on the practical aspects of parliamentary scrutiny. The subjects that are dealt with in the plenary meetings, which are drawn from the working programme of the institutions of the EU, are previously agreed at the meetings of the chairpersons of the committees for Union affairs. During the plenary meeting a contribution is adopted and sent to the Presidents of the European Parliament, the Council and the Commission.
The plenary meeting of the COSAC will be open to the public through a web-streaming.