California's three public higher education systems (University of California, California State University, the California Community College System) enroll nearly 3 million undergraduate students and employ almost 100 thousand faculty. In 2012, the California State Legislature directed the three systems to create an online library of open educational resources to encourage the use of free or affordable textbooks and other materials throughout California's public higher education system. Composed of faculty representatives from each of the three systems, the California Open Educational Resources Council (CAOERC) was formed and charged in January, 2014, with collecting, peer-reviewing, helping to curate, publicizing, and cultivating the adoption of these open educational resources. As we end the first phase of this massive effort, our paper will: 1) outline what we've learned about scale and collaboration among California's three distinct higher education systems; 2) present the results of CAOERC's ongoing research (via surveys and focus groups) about open textbook use and adoption; 3) briefly discuss issues of OER sustainability in the context of cooperation among state, university, and non-profit sectors. [This paper was presented at the "Open Education Consortium Global Conference," Krakow, Poland, April 12-14, 2016.]