What evidence counts as teacher quality is a debate of continued interest to the teacher education community. Many education scholars have argued for the importance of retention of knowledge as an indicator of the quality of education acquired. This study explored the retention of the quality of planned Topic Specific Pedagogical Content Knowledge (TSPCK) in a case study of seven chemistry pre-service teachers in their final year of study towards a BEd degree. They were exposed to a TSPCK based intervention in either Organic Chemistry or Stoichiometry as a topic and subsequently followed two years later into their practice as beginning teachers. The study employed a longitudinal qualitative research design with sets of data collected at three different points: pre-intervention, post-intervention and delayed post-intervention (two years later). Data collected included a combination of completed TSPCK tools and audio-recorded stimulated recall interviews. The analysis of completed TSPCK tools entailed the use of a criterion-based rubric for shifts in the quality of planned TSPCK and the recorded interviews were analysed through content analysis. Evidence of learning during the intervention and in-practice was analysed using the qualitative in-depth analysis for developing TSPCK and the Vygotskian sociocultural theoretical framework. Findings from the first and second sets of data confirmed a gain in the quality of planned TSPCK at the end of the intervention. The findings from the second and third sets revealed the beginning teachers' successful retention and continued growth two years in practice. Implications for teacher preparation are discussed.