The proliferation of English-medium instruction (EMI) in nonnative English-speaking (NNES) contexts has compelled researchers to explore the challenges students face in such environments. Mostly quantitative in nature with foci on language-related difficulties in one type of institution or curriculum, these studies obscure the complexity of NNES students' learning of content via English. Through the lens of "affordance" in van Lier's (2000, 2004a, 2004b, 2007, 2008b) ecology of language education, this qualitative case study examines learning opportunities afforded by two types of EMI contexts in Taiwan: selective EMI courses and an immersion program. Findings showed that despite the limited attention to cultural affordance, more content and language affordances were cognized and acted on in the design where students displayed more interest in subjects, instructors held higher expectations, and flexibility in selection of courses was allowed. As such, this paper underscores the primacy of interests, educational levels, and background knowledge in individual factors; the provision of sufficient English and cultural affordances in contextual factors; and the dynamics between the two in students' learning of content via English.