The use of English in international communication has focused scholarly attention on L2 learners' development of interactional competence (IC), that is, the ability to co-construct interactions purposefully and meaningfully in specific contexts. Under Hong Kong's bilingual education policy, students mainly learn and speak English in two classroom contexts: (1) English language and (2) English-medium-instruction (EMI) content-area subject lessons, which may contribute to their IC development. This study compared the English-speaking/learning experiences of students in these two classroom settings in three Hong Kong secondary schools. Task-based language teaching (TBLT) was the recommended teaching approach in the English language subject in all these schools, but they adopted different medium-of-instruction arrangements in content-area subjects. Their students also had different academic attainments. The investigation adopted a case study approach consisting of a questionnaire and semi-structured focus group interviews (N = 160). Our findings suggest that students generally lacked opportunities to speak English, regardless of the specific school-based policies. The higher-proficiency students were given more opportunities to speak English in group/pair activities both in English language and EMI content-area subjects. In contrast, the lower-proficiency students received more explicit teaching of the linguistic forms/structures required in English examinations. The paper concludes by highlighting several critical issues concerning students' IC development in bilingual education, namely, the effects of English-medium education on students' speaking ability, implementation of TBLT, the influence of examinations on teaching practices, and teachers' role in promoting students' interactional competence through classroom interactions. Copyright ©2023 Wiley.