In recent years, there has been growing interest in the use of data-driven learning (DDL) in L2 writing instruction. This paper examined whether and to what extent DDL activities could enhance the writing complexity, accuracy, and fluency (CAF) of 30 Thai EFL learners. The presentation of DDL in this study was hands-on concordancing with the assistance of the Corpus of Contemporary American English (COCA). The study was held in the context of an English writing workshop focusing on opinion paragraphs, divided into two phases: four weeks for the pattern-hunting activities and two weeks for the pattern-refining activities. Applying the CAF Profile of Larsen-Freeman (2006), the pretest and posttest writings were analyzed. The results showed that DDL can enhance learners' writing lexical complexity, accuracy, and fluency, whereas no statistically significant evidence was found in terms of grammatical complexity. Furthermore, the results from the questionnaire and the interview indicated that the learners had positive attitudes towards DDL as a useful reference resource to enhance their vocabulary acquisition, refine their writing, revise their compositions, generate fresh ideas for writing, and boost their writing confidence. These findings underscore the potential of DDL as a pedagogical tool in L2 writing instruction.