This study evaluates the development of L2 collocational competence in texts written by learners of differing proficiency levels, compared to native speaker collocation patterns from a reference corpus. We address: (1) whether learners develop their collocation competence as their proficiency grows; and (2) How is this development mediated by different aspects of collocability, i.e., exclusivity, directionality, and dispersion? Effective quantitative metrics based on the native corpus were assigned to each bigram type in L2 texts, covering important aspects of collocability. Correlations between the text-based average scores of each metric and L2 proficiency were analyzed to examine the development of collocability in each dimension. Our results show that exclusivity increases with learner proficiency. When directionality is considered, learners develop native-likeness in forward-directed word selection across all levels; backward competence, however, improves more markedly at advanced levels. Our analysis also suggests learners start to use less deviant collocation patterns but more domain-specific bundles as their proficiency grows.