It is assumed that open and distance learning institutions develop study materials that adequately engage learners with quality content to assist their content mastery. However, distance learners continue to underperform, which raises the concern that high drop-out and failure rates may be ascribed to the study materials. This mixed-methods case study examined instructional material developed for secondary school learners studying via the open and distance learning mode. The study was informed by Sweller’s Cognitive Load Theory to evaluate the process of designing and developing instructional materials while Gorsky, Caspi and Trumper’s Theory of Instructional Dialogue was used to map interaction with and within the selected study materials. A self-designed evaluation rubric included language-related criteria to gauge the accessibility of content. A questionnaire survey was undertaken with purposively identified participants: five material developers, 176 learners, and six tutors. Six semi-structured group interviews and twenty individual face-to-face interviews were conducted. Open coding and SPSS reports were used for qualitative and quantitative data analysis, respectively. Findings related to non-alignment of materials with learner profile, and the national syllabus, while inadequate proficiency in the language of instruction remained problematic. The
outcomes of this study highlight the importance of well-trained material developers
and focused ODL policies for quality assuring effective content design and
development to accommodate diverse learners with limited English proficiency.