Despite Iran's rich tapestry of ethnic, religious, and gender diversity including Kurds, Arabs, Balochis, Turkmen, Armenians, Assyrians, Jews, Zoroastrians, Sunnis, as well as women and girls in their full societal roles educational materials in the country have often been criticized for their homogenized portrayal of national identity. This study critically examines the representation of marginalized voices in Iranian English as a Foreign Language (EFL) textbooks, specifically focusing on the Prospect series (Prospect 3), which are widely used in Iranian secondary schools. Adopting a qualitative research design grounded in Van Dijk's (2001) multimodal critical discourse analysis framework, this study investigates how ethnic, religious, and gender minorities are represented or systematically excluded across textual, visual, and discursive dimensions of these textbooks. Data were collected through comprehensive content analysis of all six lessons, review sections, photo dictionaries, and supplementary materials within Prospect 3, utilizing a seven-code coding scheme. Findings reveal a complex pattern: while girls and women appear frequently in visual materials (as students, mothers, tourists, and patients), their narrative roles remain largely confined to domestic, supportive, or caregiving positions, with few representations in professional or leadership capacities. In contrast, ethnic and religious minorities are almost entirely invisible, with all character names being exclusively Persian and no representation of minority cultural or religious practices. Foreign nationals (German, Turkish) appear in travel dialogues, yet Iranian internal ethnic and religious diversity remains completely erased. The study discusses the implications of these representational patterns for students’ identity formation, sense of belonging, and understanding of diversity. Recommendations for inclusive curriculum reform are provided