This corpus-driven longitudinal study investigates the structural use of lexical bundles in published research article (RA) introductions in applied linguistics written by English experts and Korean graduate students across two different levels of study. Frequency-based bundles were retrieved from a corpus of 200 published RA introductions and two corpora of 46 and 49 introductions of term papers written at two time points of the first and fourth semester of graduate course. In a further step, the structures of the bundles in different rhetorical moves of RA introductions were analyzed to reveal the developmental patterns in bundle use. The analyses show that the Korean graduate students are in the developmental process of academic writing featured by a shift from clausal style to phrasal style as their academic level advances. The results also suggest that the students have difficulty in appropriate bundle use in specific rhetorical moves even at the later academic level of graduate coursework. The pedagogical implications of L2 students’ developmental order are discussed.

Lexical bundles have been widely investigated as an indicator of English for Academic Purposes (EAP) writing development in terms of structure and function by exploring the use by students compared to experts. However, little research has compared the use of lexical bundles by second language (L2) Korean EAP students across different academic levels versus first language (L1) English experts with longitudinal corpora. The current study addresses this gap by comparing lexical bundles used both two L2 student corpora and English L1 corpus consisting of introductions of research articles (RAs) and those of term papers. The findings showed the Korean graduate students are in the developmental process in the use of lexical bundles as their academic level advances. However, noticeable development was not found between the students at two levels in terms of function unlike in terms of structure. The pedagogical implications are discussed regarding structural and functional use of bundles for Korean EAP students.