The present study investigates the use of English lexical collocations and their relation to the online writing of Taiwanese college English majors and non-English majors. Data for the study were collected from 41 English majors and 21 non-English majors at a national university of science and technology in southern Taiwan. Each student was asked to take a 45-minute online English writing test, administered by the web-based writing program, Criterion Version 7.1 (Educational Testing Services) to examine the subjects' use of lexical collocations (i.e., frequency and variety). The test was also used to measure writing fluency of the two student groups. Test results were examined to answer the two major questions for correlation (1) between the subjects' frequency of lexical collocations and their writing and (2) between the subjects' variety of lexical collocations and their writing. The study findings indicated that: (1) there seemed to be a positive correlation between Taiwanese college EFL learners' frequency of lexical collocations and their online writing scores; and (2) there seemed to be a significantly positive correlation between the subjects' variety of lexical collocations and their online writing scores. This present study also reports on a pattern of lexical collocation development observed among writers of different fluency levels, ranging from the lowest to the highest. Appended are: (1) Empirical Studies on Collocation Error Analysis; and (2) Scoring Guide by Criterion (7.1), ETS (http://criterion-cs.ets.org.) (Contains 5 tables, 1 figure, and 6 footnotes.)