Teachers' pedagogical content knowledge (PCK) importantly contributes to instructional quality and student outcomes. We aimed to complement the limited insights into preservice preschool teachers' PCK, and its association with opportunities to learn (OTL), during teacher training. We offered 162 first-to-final-year preservice preschool teachers from two different teacher training institutes in Flanders (Belgium) a recently developed scenario-based instrument addressing students' understanding of preschoolers' (mis)conceptions and appropriate instructional strategies in the domain of early mathematics. Our findings revealed quantitative differences between first-year students' PCK on the one hand and second-year and third-year students' PCK on the other hand. We did not observe any quantitative differences in PCK between second-year and third-year students. Additional analyses on students' errors pointed to qualitative differences between first-, second- and third-year students' PCK. We interpret these findings in view of students' OTL during teacher training, and discuss their theoretical and methodological implications for future work in the domain of teacher competence.