Using the academic writing sub-corpora of the Corpus of Contemporary American English and the British National Corpus as data and building on previous research, this study strives to identify the most frequently-used multi-word constructions (MWCs) of various types (e.g., idioms, lexical bundles, and phrasal/prepositional verbs) in general academic writing across the academic divisions of the corpora and to examine their usage patterns. The study produces: (1) a list of the 228 most common MWCs in general academic written English across the academic divisions in the corpora, organized by frequency and semantic function respectively, (2) new findings regarding the usage patterns of academic written MWCs, and (3) results about differences in the use of MWCs between American and British English. The study also demonstrates the critical importance of using large corpora in the study of MWCs in general academic writing. (Contains 3 tables.)