The present study aimed to examine the rhetorical structure of the discussion sections of English PhD dissertations authored by Iranian students in an EFL context, Indian ESL students and native (English speaking) PhD students at Applied Linguistics. To this end, 300 discussion sections were gathered from three contexts under study at the time frame of 2005 to 2020. Following Benson et al’s (1986) model, the researchers analyzed the discussion sections of the dissertations for both lexical and grammatical collocations and their different sub-classifications. The findings showed that the natives overused collocations in a significantly greater number in developing the PhD dissertations discussion section than those of EFL and ESL PhD students' dissertations. Moreover, despite variations, there were similarities between EFL and ESL PhD students' dissertations in terms of utilizing the sub-categories of collocations that can be considered as signs for standardization of academic writing by non-native speakers of English. The implications for researchers, teachers and students were discussed. تفاصيل المقالة