This study examined the development of automaticity in processing L2 collocations, and the roles of L1 collocational knowledge and practice conditions in the development process. Korean learners of English were assigned to one of two practice conditions (practice in identical or varied contexts). The learning gains for word combinations with and without equivalent counterparts in the L1 (L1-only and L2-only collocations) were assessed using response times (RTs) and coefficients of variation (CV) from a phrasal decision task. The results demonstrated that the learners in both groups showed significantly improved collocation processing for both types of items in terms of speed (RT) and automaticity (CV) over time. The RT and CV analyses indicated that both groups’ improvements in collocation processing in the later stages of learning were associated with automatization. Interestingly, L1 collocational knowledge played a facilitative role in processing speed only in the early stages of learning. No reliable evidence for the differential effects of the two types of practice conditions on developing automaticity in collocation processing was found.