Many under-prepared university students do not know how to study (Martin and Arendale 1993) because they have not yet developed the abstract reasoning skills that allow them to learn new ideas simply by reading a text or listening to a lecture. This article draws from selected findings from a PhD study currently being undertaken at a university in KwaZulu-Natal. This article explores the use of Supplemental Instruction (SI) in supporting deep understanding and higher-order thinking skills (HOTS) in stoichiometry in first year chemistry for engineers. The special focus of this article is to investigate whether the quality of teaching and learning in chemistry education is improved through SI and SI leader intervention. The central question guiding this article is: How does an interactive teaching and learning intervention programme (SI) facilitated by SI leaders potentially engage first year engineering students in deep understanding and HOTS in Chemistry? Since this article focuses on change or growth in natural settings, within stoichiometry in chemistry classrooms, it allowed for video-recordings, observations of SI sessions and focus group interviews which have been used in this study. Data analysis revealed that students preferred the more interactive engagement of SI sessions and discussion around chemistry concepts. Students found that having to explain concepts in their own words and being exposed to other students methods of answering questions greatly improved their understanding of stoichiometry. It was also found that SI leaders encouraged HOTS by asking higher-order questions, engaging in activities that required higher-order thinking as well as encouraged students to reflect on their thinking. It is therefore argued that teaching and learning strategies employed during the SI intervention session have the potential to promote deep understanding and higher-order thinking. (Contains 3 tables and 2 figures.)