This document summarizes research on the emerging field of open educational resources (OER) over time. It analyzes the content of OER publication abstracts from 2007 and 2015 to identify common categories and how the field has changed. The categories identified include project case studies, technical focus, OER as a subject, research with impact data, policy, practitioners, MOOCs, pedagogy, and open data/practice. It finds that practitioner focus, MOOCs, and policy have grown as categories while case studies have declined. The field has diversified into related areas and reflects a maturing community with policy and sustainable practices.