This study examined acquisition order disparities and their associated causes in an EFL context, so that pedagogical means of enhancing the process of morphosyntactic development could be discovered. Twenty-six South Korean EFL middle school students were given an extensive timed writing test. Following the administration of this test, an acquisition order for 16 morphosyntactic features was constructed. The EFL order was first compared to others found in ESL contexts. It was then compared to six hypothesized causes of acquisition: EFL input frequency, L1 similarity, morphosyntactic variability, semantic complexity, sonority, and morphosyntactic complexity. Results suggest that while input frequency and L1 similarity are the most significant predictors, all causal variables have a role in the manifestation of acquisition order within an EFL context. Suggestions for curricular reform that utilize the unique causal characteristics of each morphosyntactic feature have been proposed.