Despite the proliferation of research on how second language (L2) learners engage with feedback on L2 writing in recent years, little is known about how young and low-proficiency L2 learners process teacher feedback. The present study investigated how Chinese lower-secondary school learners of English as a foreign language (EFL) cognitively and behaviourally engaged with teacher feedback in two conditions: individual written languaging and collaborative oral languaging. Eighty-one students (aged 13–14 years, A1–A2 English proficiency) from two classes and two English teachers at a public lower-secondary school in China participated in this study. Comprehensive teacher feedback (focusing on language errors, content, and organization) was provided to students on three writing tasks completed over six weeks. Findings showed that collaborative processing of teacher feedback elicited students’ deeper cognitive processing, drew their attention to issues beyond linguistic errors and encouraged learner autonomy. On the other hand, individual written languaging promoted students’ noticing of teacher feedback in their languaging process, although with a primary focus on grammar and mechanics. Written languaging also enabled students to act on more teacher feedback points in their revisions than the collaborative processing condition. Pedagogical implications from the comparison of the two feedback processing conditions are discussed.