Article 21 (2.c) of the Lisbon Treaty states that "the Union shall define and pursue common policies and actions, and shall work for a high degree of cooperation in all fields of international relations, in order to preserve peace, prevent conflicts and strengthen international security, in accordance with the purposes and principles of the United Nations Charter, with the principles of the Helsinki Final Act and with the aims of the Charter of Paris, including those relating to external borders."

The EU and the OSCE share a strong interest to co-operate on security-related discussions and conflict prevention in Europe and co-operate closely at all levels, including in the field. The EU and the OSCE pursue a permanent political dialogue among their members and coordinate efforts in pursuing common objectives and finding shared solutions. The agendas of the two organisations overlap to a considerable degree.

In 2018, the EU and the OSCE exchanged letters, at the level of Secretary General, agreeing to strategically strengthen their institutional interaction, as well as their operational co-operation in areas of common interest across the three dimensions.

The EU actively supports this comprehensive and co-operative approach to security. As the Common Foreign and Security Policy of the EU grows in importance and effectiveness, especially with the development of a European Security and Defence Policy and of a crisis prevention and civilian crisis management capacity, the co-operation between the EU and the OSCE increases. The EU also greatly values the role of OSCE field operations and the autonomous OSCE institutions.

EU Member States contribute more than two thirds of the OSCE's main budget and the EU and EU Member States also contribute to the funding of a number of OSCE implemented extra-budgetary projects. Examples of EU support for the OSCE include assistance for the ODIHR in developing national electoral and human rights institutions and crisis management, for instance in the Western Balkans.

The EU Delegation to the International Organisations in Vienna coordinates the EU policies in the OSCE on a day-to-day basis and represents the EU in the OSCE.

The key features of the EU's participation in the OSCE are:

• The Delegation of the EU is regarded as being part of the Delegation of the OSCE participating State holding the rotating Presidency of the Council of the EU. As such the Delegation is participating in all proceedings unless the issue under discussion clearly falls fully outside the scope of the EU.
• As the EU has its own Ambassador/Permanent Representative  accredited to the OSCE, it is, in principle, treated as an individual OSCE participating State as concerns protocol issues, and as regards the circulation of documents or other information or invitations.
• In all OSCE decision-making bodies, including on Ministerial and Head of State and Government level, the EU has a seat reserved beside the country holding the rotating Presidency of the Council of the EU (in non-decision-making bodies the question does not arise as the OSCE practices 'free seating').
• In cases where the issue under discussion mainly falls under the competence of the European Community, the Delegation of the EU, representing also the Commission, can intervene in the same way as an OSCE participating State.
• In OSCE decision-making bodies, where the EU is speaking 'with one voice', the EU Delegation may speak on behalf of all EU Member States.
• In non-decision-making bodies, the Delegation usually coordinates the position of all EU Member States and presents it in meetings.
• At meetings at the levels of Ministers or Heads of State and Government, the EU High Representative or the Presidents of the Council or Commission intervene.  

In particular through its Delegation accredited to the OSCE, the EU has developed close contacts both with other OSCE Delegations and with all OSCE Institutions, notably the OSCE Secretariat in Vienna as well as the OSCE Office for Democratic Institutions and Human Rights (ODIHR) in Warsaw. Although the EU as such cannot contribute to the Unified Budget of the OSCE, it has become in recent years a big donor of extra-budgetary contributions for a large variety of programmes and projects.

The close relations between the EU and the OSCE are also maintained through regular meetings, from EU-OSCE Ministerial Political Dialogue meetings to PSC-level Political Dialogues and staff-to-staff talks. At field level, there are regular contacts between the OSCE field missions and the respective EU Delegations, as well as the CSDP Missions of the EU. In addition, the EU works with the OSCE and other partners in the conflict resolution processes in Moldova and in Georgia.