The Organization for Security and Co-operation in Europe (OSCE) is the largest regional security organization, with 57 participating States from Europe, Central Asia and North America. Mongolia is the latest to have joined the OSCE family in 2012. Yet, despite its size, the OSCE and its role in promoting peace, democracy and stability for over a billion people is not known very well. Perhaps even less appreciated is the extent to which the Organization contributes, in different ways, to preventing terrorism and countering violent extremism and radicalization that lead to terrorism. The authors summarize the OSCE’s multi-dimensional and multi-stakeholder approach to countering terrorism, pertinent past and on-going activities, and they outline a way forward that focuses more and more on tailored capacity building.