This study examines the structure of lexical bundles, a special kind of multiword expressions, to compare their uses between native speakers (L1) and two groups of Korean learners of English at the A2 (lower) and B2 (higher) proficiency levels as described in the Common European Framework of Reference for Languages (CEFR). Collected from native and nonnative corpora, lexical bundles are first analyzed in relation to three structural categories, NP-, PP-, and VP-based bundles, and then, eight sub-VP categories. Results show two structures are of pertinent interest: NP-based bundles and VPs with a that-clause. L2 writers tend to use more VP-based bundles and fewer NP- or PP-based bundles than L1 writers do, as can be predicted from the research literature. A comparison between the two CEFR levels, however, shows an unexpected contrast: the lower-level students use NP-based bundles more frequently than do the higher-level students. In regard to the VP-based bundles, the higher-level students use two particular sub-types, VPs with a that-clause and VPs with a copula be. Findings indicate that these bundles are potential criterial features for distinguishing low and high level of writing competence of Korean learners of English.