The present study aimed to profile the developmental patterns of discourse in second language (L2) writings among different first language (L1) groups. Applying the list of metadiscourse markers proposed by Ken Hyland to learner language, this study investigates variation of metadiscourse across proficiency levels, as well as across L1 backgrounds. Using the International Corpus Network of Asian Learners of English, the present study compared the frequencies of metadiscourse markers used in the writings among different learner groups. The results suggest that the six learner groups that were compared have diverse frequency change patterns of metadiscourse features across proficiency levels. To be specific, Japanese learners' heavy reliance on self-mentions and boosters is remarkably antithetical to Thai learners' preference of engagement markers and hedges. Moreover, B2 and higher level learners in China and Taiwan exhibited greater numbers of evidential patterns ("hereafter" evidentials) than learners in other groups. These differences can be attributable to their L1 rhetorical strategy, not to their lexical and grammatical competence. Therefore, we should consider the idiosyncrasies in metadiscourse of each L1 group when assessing L2 learners based on their language performance.