Previous studies have explored the roles of metacognitive instruction and collaborative writing, separately, in English writing. Little attention has been paid to students' writing complexity, accuracy, and fluency (CAF). The present study aims to bridge this gap through investigating integrated writing performances based on the linguistic features of CAF. The focus was on four groups: metacognitive instruction in a collaborative-writing setting (n = 84), metacognitive instruction in an individual setting (n = 88), collaborative writing (n = 96), and individual writing (n = 84). The formation of the four instructional groups was based on the combination of the components: Metacognitive training and collaborative/individualized writing condition. All participants were Chinese tertiary-level EFL students. They were asked to complete an argumentative essay, following which the learners in the four groups were assessed and compared in terms of CAF. The results based on MANOVA revealed that the interplay of metacognitive instruction and collaborative writing exerted a positive influence on writing accuracy, but not on fluency and complexity. The transcripts based on pair dialogues illuminated the writing process and the language-related episodes. The present study provides theoretical and practical implications for metacognitive instruction and collaborative writing. The findings exemplify writing CAF.