This paper introduces the Chinese Learner English Corpus (CLEC), comprising argumentative texts written by Chinese lower and upper secondary school students. CLEC expands learner corpus research by including texts from intermediate-level learners and rich metadata on their backgrounds, including engagement with self-initiated, so-called Extramural English (EE) activities outside the classroom. To illustrate potential uses, two case studies are presented. The first uses a keyword analysis to reveal thematic and stylistic differences between CLEC and its Swedish counterpart, SLEC, highlighting linguistic priorities related to distinct learning contexts. The second investigates lexical bundles associated with gaming, demonstrating how EE engagement might influence learners’ use of multiword units. Freely available online, CLEC facilitates contrastive interlanguage analysis and supports further research into L2 learning and use, particularly regarding the role of language exposure. The corpus is also a valuable resource for teacher trainees aiming to deepen their understanding of SLA processes.