The Internet has been conducive to English as a foreign language (EFL) students' agency. However, EFL learners' agency does not necessarily make them autonomous learners, although agency and autonomy are interchangeably used. By addressing the link and difference between these two constructs, this qualitative exploratory case study sets out to explore how a blended-designed course mediates Turkish EFL high school students' autonomy development scaffolded by Moodle LMS during the 2018-2019 academic year. The sociocultural theory forms the theoretical prism of the study. The data, collected via semi-structured interviews and reflective journals, were analyzed via grounded theory. The findings revealed that students enjoyed metacognitive, socio-cognitive, and socioemotional benefits. The main pedagogical implication to be drawn from this study is that LMSs could be employed to transform the students' existing agency into autonomy. Theoretical implications are discussed in light of the post-pandemic period and technological affordances.