Work in corpus linguistics has led to the development of a theory of language as "phraseology" [Hunston, S., & Francis, G. (1999). "Pattern grammar: A corpus-driven approach to the lexical grammar of English." Amsterdam: John Benjamins. Sinclair, J. M. (1991). "Corpus, concordance, collocation." Oxford: Oxford University Press. Sinclair, J. M. (2004). "Trust the text: Language, corpus and discourse." London: Routledge.]. This paper investigates whether and to what extent phraseology, as exemplified by the grammar patterns "it" v-link ADJ that- (e.g. "It is clear that the problem of evidence continues to vex new historicist criticism") and "it" v-link ADJ to-inf (e.g. "it is important to compare unemployment rates on a consistent basis"), varies or remains consistent across four multi-million word corpora representing two different genres (research articles and book reviews) and two different disciplinary discourses (History and Literary Criticism), and is therefore at least partly constitutive of these generic and discursive formations. A quantitative analysis of the corpus data reveals significant and systematic distributional trends across both genres and disciplines, and a qualitative analysis of concordance lines confirms that these trends are not arbitrary but motivated by genre-specific purposes and discipline-specific practices, respectively. The paper concludes with a discussion of the theoretical and pedagogical implications of the study, and by making suggestions for further research. (Contains 6 tables.)