This chapter reviews the quantitative corpus linguistic literature on formulaic language development in writing. It first provides a theoretical and methodological context by discussing the construct of formulaic language and the various ways in which it has been operationalised in studies of writing development. It then critically reviews the literature to establish what substantive conclusions can be drawn and what might constitute productive foci for future research. The review highlights a lack of interest in first-language studies. However, second-language studies have seen a rapid expansion of interest over the last decades, which has yielded a number of consistent patterns. In particular, writing quality is positively associated with the percentage of n-grams attested in a reference corpus, the mean strength of association between collocates (again as attested in a reference corpus), and the prevalence of sequences which analysts subjectively identify as formulaic. It is also negatively associated with use of formulas copied from source materials. Key areas in which further methodological development is needed include: understanding how analysts identify sequences as formulaic; increasing the size and rigour of studies looking at discourse functions of lexical bundles; understanding the impact of reference corpus on findings; developing corpora representative of learner input.