In South Africa, poor performance of learners in mathematics across the school system is a problem demanding new solutions. One possible solution is to try to raise standards through the use of open educational resources (OER). This article presents and discusses findings from a case study of a collaborative OER development project initiated by the South African Institute of Distance Education (SAIDE). In this project mathematics teacher educators from nine tertiary institutions worked collaboratively in designing OER for mathematics teacher education courses and use in a variety of other contexts. The study investigated whether the collaborative redesigning of existing materials can enhance quality while containing time and resource costs and whether such collaboration encourages buy-in to the use of OER by teacher educators and students. It concludes by offering some suggestions on OER development for policy-makers, practitioners, and researchers in the field of distance education. (Contains 1 table, 1 figure and 1 note.)