Content-based instruction (CBI) has been proposed as an effective method of preparing students for study in English-medium universities. Although CBI has won adherents for its pedagogical effectiveness, a theoretical basis for its success has not been fully articulated. There are a variety of frameworks that may be used to provide this theoretical basis. This paper argues that an ecological framework on language learning and use can provide this theoretical underpinning. A content-based English pre-sessional course illustrates the proposed ecological framework. The course, using a textbook for native-English speaking undergraduates [Seitz, J. L., (2002). "Global issues: An introduction". (2nd ed.). Oxford & Malden, MA: Blackwell], helps students learn the expectations of university study through extended focused reading, discussion and writing. In this way, EAP skills are contextualized in an integrated learning process.