Using the already validated Coh-Metrix tool, this thesis examines whether there are significant linguistic and discourse differences between journal s written by Iranian, American and British researchers. To identify the language varieties between the academic s written by Iranian researchers and their native counterparts, 450 English s written in the fields of dentistry, electrical power engineering and applied linguistics by Iranian, American and British writers were analyzed based on the five principal components of narrativity, referential cohesion, syntactic simplicity, word concreteness, and deep cohesion. The results of the discriminant analysis demonstrated that the s written by Iranian researchers were less in the structure of lexicon compared with those written by American and British researchers. Regarding the disciplines, our study provided evidence that Iranian authors used significantly more words in the field of electrical power engineering. In the field of dentistry, the s written by Iranian writers largely followed British writing style. The results indicated that the American writers tend to use higher deep cohesion and British authors used significantly more difficult syntax. In the field of applied linguistics, the results showed that the British writers tend to employ more difficult syntax. In this field the s written by Iranian writers were more similar to American writers. Our conclusion is that it is reasonable to assume that the s written by Persian native speakers had minor deviations from proto-typical style of the English register. This study sheds light on language varieties and methodology that may be helpful to English as a Second Language Learners as well as materials developers, teachers and researchers in non-English-speaking countries such as Iran. Keywords : language varieties; Coh-Metrix; writing; Contrastive Corpus Analysis; Cohesion