In this paper, we explore the challenges towards the adoption/use of Open Educational Resources (OER) within the Greek Higher Education (HE). To achieve this objective, first we present “Kallipos”, a large-scale open access textbook publishing initiative that was launched in 2013 by the Hellenic Academic Libraries Link (HEAL-Link) consortium. Then, we analyse and interpret the results of two surveys performed at the outskirts of this project. The first survey, committed among faculty members that authored or peer-reviewed an open textbook, highlights the barriers they faced, as well as the teaching and learning benefits from OER adoption/use. The second survey, addressed to university administrative executives (Deans of Schools), identifies their views about the OER usefulness and further development. The empirical data were collected by the use of two questionnaires. The findings align with the results of the current European and international research, thus are usable not only by the national but also by the international policy makers and educational leaders. We conclude by summarising the main lessons learned by “Kallipos”, and by suggesting specific proposals for the sustainable continuation of the action guided by strategies for its potential international scope expansion.