Many studies have addressed the issue of collaborative teaching in EAP courses; however, there is a gap in the literature concerning EAP teachers' cognitions and actual practices regarding collaborative EAP teaching, especially in contexts like Iran where EAP courses are taught by either language teachers or content teachers - subject specialist teachers - with little or no cooperation between them. Therefore, the current nationwide study explored the cognitions and practices of language teachers and content teachers at medical sciences universities in Iran regarding collaborative EAP teaching. The participants were 128 representative language teachers and 190 representative content teachers, teaching at all five types of universities across the country. The instruments included questionnaire and semi-structured interviews. The results revealed that the differences between the two groups of EAP teachers overshadow the similarities between them. The findings also disclosed inconsistencies between the two groups of EAP teachers in terms of their cognitions and actual practices. The conclusions outline implications for the EAP community throughout the world and specifically accentuate the urgent need for teacher education programs in Iran and micro- and macropolicy reforms in the Iranian EAP educational system.