Although English language teaching (ELT) textbooks have been investigated from various cultural perspectives, religion as a significant aspect of culture has rarely been addressed in materials evaluation studies. To fill this lacuna, the current study draws upon the Cultural Linguistics semiotic analysis (Dinh, Sharifian (ed.), Advances in Cultural Linguistics, Springer Nature, 2017) to explore the representation of religion in locally developed ELT textbooks in Iran, namely Prospect and Vision series. Content analysis of texts, tasks, and visuals of these two series revealed different instances of Islamic cultural schemas and categories though no cultural metaphor in relation to religion was identified. The findings unveiled light of a hidden curriculum that advocates the Iranian government's ideology and the exposure to the local variety of English in Iran that is limited to religious topics.