Open educational resources (OERs) have wide-ranging implications for education by influencing relationships between teachers and students, students and institutions, and knowledge and society. OERs are part of profound changes in knowledge practices such as open data, open scholarship, and open source. However, assessing the impact and use of OERs is challenging as openness makes quantitative tracking difficult and qualities of use and outcomes are hard to evaluate, especially because reuse may occur in invisible or personal contexts. Different approaches are needed like tracking specific OERs, investigating user experiences, and deconstructing the qualities of open content and practices.