Recent research has highlighted the value of providing metacognitive guidance for learning English in a small group setting. This study investigated the effects that the presence or absence of metacognitive prompts for group or individual learning could have on reading comprehension and the incidental learning of vocabulary through reading. A total of 171 university students were randomly assigned to four treatment conditions: collaborative learning with metacognitive prompts, collaborative learning without metacognitive prompts, individual learning with metacognitive prompts, and individual learning without metacognitive prompts. Results indicated that after the treatment, learners in the collaborative learning with metacognitive prompts group outperformed the other groups on both reading comprehension and incidental vocabulary learning assessments. In addition, the vocabulary knowledge acquired by students in the collaborative learning with metacognitive prompts group was highest for meaning recognition, followed by form recognition, meaning recall, and finally form recall. These findings highlight the importance of training students' self-regulated learning and suggest that the use of metacognitive prompts in a group setting is an effective means to boost EFL reading comprehension and the incidental vocabulary learning for Chinese university students. Pedagogical implications of these and other nuanced findings are discussed.