Taking a usage-based approach, this paper aims to define conventionalized ways of saying things (CWOSTs) as multi-word units so that they can be included in researching L2 development. It builds on Langacker's (2008) “normal ways of saying things“, here understood as conventionalized form-meaning-function mappings. It uses task-elicited written texts from 40 Dutch L2 learners of English to obtain a range of possible ways of expressing the same notion. Each expression was judged for naturalness by native speakers of English and checked for token frequency in reference corpora. Based on these two measures of conventionalization, CWOSTs can be captured as the preferred formulations among a range of possible ways of expressing the same beyond-word-level notion. It is concluded that in L2 development, conventionalized ways of saying things (CWOSTs) are best defined against awkward ways of saying things (AWSTs); compare when I grow up and when I am a grown up adult.