This article reports on a mixed-method research into the representation of source culture in an English language textbook series used at a major university in the Arabian Gulf. The current study utilized Ideology Critique Methodology and was framed within the Critical Research Paradigm. The research used a structured questionnaire, followed by open-ended questions administered to 30 purposefully chosen language teachers. The study attempted to ascertain, in the light of Muslim teachers' perceptions, the representation of Islamic (and Saudi) culture, the extent of a multicultural outlook, and presence of any culturally inappropriate or offensive material in the contents of a most popular English language textbook series. The study endorsed the idea of "appropriation" of English according to variable contexts and opposed predominance of western culture in TESOL course books at the expense of local cultures.