Drawing on a comprehensive literature review of best practice in OER measurement, as well as experience of working with UNESCO to support implementation of the Recommendation, this chapter presents an initial framework for the measurement of the effectiveness of the OER Recommendation and proposes indicators that regions, countries, and/or institutions could adopt or adapt to rigorously measure both how OER is used and its effectiveness for improving learning. Putting in place shared understandings of what counts as effectiveness for OER is critical to inform ongoing developments and improvements in the field. Such measures can also provide an evidence base that can be used for advocacy work around the importance of OER for quality open and distance learning.