This is a research report of a one-year study which addresses whether and in what way grammatical CALL can help English writing instruction in an EFL setting, namely, in Taiwan, R.O.C. The study started with the implementation of CALL courseware which contains ten lessons of grammar exercises. The courseware featured (a) empirically based contents, results from error analysis of Chinese EFL students' common mistakes; (b) a sentence-level drill and practice with various formats of guided Chinese-English translation, error correction, and sentence combining; (c) adaptive remedial instruction for individual students while practicing on-line; (d) integration of error anticipation and keyword matching for answer judging as well as item-specific feedback messages; and (e)verbatim recording of student input. To evaluate the effectiveness of this CALL strategy, we designed an experimental study in which two groups of college freshman EFL majors did the pre-test and post-test tasks with ten-week CALL intervention for the experiment group while the control group worked on the same contents in a paper-and-pen homework setting). Results suggested that the combined effect of classroom instruction and grammatical CALL is helpful for writing instruction, or at least not detrimental.