By adopting a usage-based approach to language acquisition, this study investigated the emergence and development of L2 constructional knowledge. A total of 19 English verb-argument constructions (VACs) and their associated verbs were extracted from a learner corpus and three verbal fluency tasks, each conducted in L1 and L2 English and L1 Korean. We compared verb usage in the target VACs across proficiency levels between the L1 and L2 groups and between data types for VAC productivity and verb-VAC associations. The results identified three stages through which Korean learners' VAC knowledge develops in L2 English: emerging through the frequent use of a few general verbs, expanding the range of verbs associated with a VAC to include more specific and prototypical verb types, and then developing them into a creative constructional schema. Moreover, we determined similarities between L1 and L2 English VAC knowledge in higher L2 proficiency levels, as well as L1 Korean influences related to L1 typology and L1 collocational transfer.