This study explores how second language (L2) postgraduate writers from different disciplines at a Mexican university negotiate feedback on concerns about the structure of academic research genres (e.g., conference proposals, journal articles) with professional writing center tutors based in the United States, and it reports on those writers' main concerns and communicative skills. Five L2 volunteer writers with an ongoing draft for publication and academic writing needs in English participated in synchronous online tutoring sessions and follow-up interviews, which were later analyzed in a contextual and deductive way. Findings revealed that concerns at a discourse level (e.g., organization, flow) were predominantly addressed during the tutoring. Moreover, concerning negotiation, Experimental Sciences L2 writers generally agreed and gave short answers to tutors' questions as opposed to the Humanities and Social Sciences writers, who provided more explanations. Findings suggest L2 writers across disciplines need training in academic writing skills to manage concerns at a discourse level, and the Experimental Sciences writers need negotiation skills to interact with feedback and manage writing from a collaborative perspective as Canagarajah & Jerskey (2009) argued.