This research investigated the realization of collocation in two respects: how collocation was formed
appropriately and inappropriately in written texts. Following Benson et al. (1997), Lewis (2001), and Mahvelati
& Mukundan (2012), the research categorized collocation into two major types, lexical and grammatical
collocation. Text analyses conducted largely qualitatively indicated that out of seven subtypes of lexical
collocation used appropriately, three combinations (v+n, adj+n and v+adj) were predominant and out of four
subtypes of grammatical collocation realized, two combinations (prep+n and v+prep) were the major ones. It
was also shown that more collocations were used, and fewer errors were made as the proficiency levels got
higher. Therefore, the realizations of collocation in the two respects are linked to the writing quality.
Keywords: collocation, lexical collocation, grammatical collocation, EFL, proficiency level