Beyond first-year composition, the undergraduate mechanical engineering curriculum provides few opportunities for students to develop technical writing skills. One underutilized path for students to strengthen those skills is the required sequence of laboratory courses, where students write reports that are evaluated by graduate teaching assistants (GTAs), many of whom speak English as a second language. Historically, engineering GTAs have not been trained in formative assessment techniques to help students improve their technical writing skills. This dissertation details a comprehensive study of a GTA training program implemented in a large mechanical engineering department. Situated within the field of Writing Across the Curriculum/Writing in the Disciplines, the program was developed to meet the unique needs of the department’s GTAs and address perceived deficiencies in undergraduate student writing by teaching best practices in writing evaluation. Two methods were used to assess the efficacy of this program: 1) Qualitative methods such as interviews and an open-ended survey were used to gain the perspective of the GTAs and their students on a variety of issues; and 2) A summative assessment compared Senior Capstone Design final reports completed prior to the program’s implementation to reports completed three years later to gauge improvement in clarity and concision. This research is relevant to engineering programs seeking to improve the communication skills of their undergraduate students. The program used limited staff/faculty resources to extend the knowledge and skills of its GTAs and reach all its undergraduate students through existing required courses