This main event is usually held in early September and attracts over 300 delegates from the UK, Europe, North America and elsewhere. The most recent annual conference was OR51, and was held on 8 - 10 September 2009 (the next is OR52). The three-day conference programme contains a mixture of plenary sessions given by keynote speakers and parallel streams, covering all aspects of OR. In addition there is a comprehensive social programme.

Every other year the Society holds this conference, intended for young academics and practitioners with up to ten years' experience in OR. The most recent was Young OR 16, and Young OR 17 takes place on the 5 – 7 April 2011. It gives younger members of the profession an opportunity to present their work in a non-threatening environment to an audience of their peers. There are plenary talks by keynote speakers, interspersed with parallel streams and a comprehensive evening social programme.

Each year, the society holds a variety of one and two-day conferences on specialist topics. In recent years conferences have covered such areas as the evaluation of investment in Information Technology, the role of analysis in  Business Process Re-engineering, the use of simulation in healthcare, and developments in Soft OR methods.

Recent, present and future conferences include: KMAC 2006 - the Knowledge Management Conference, the European Conference on Intelligent Management Systems in Operations (IMSIO 4), a two-day Simulation Workshop (Simulation Workshop 2010), and a Tribute to Jonathan Rosenhead at 70.