This study aims to investigate how engineering undergraduates perform writing transfer from first-year composition (FYC) to engineering writing-in-the major courses. A sample of seventeen engineering students' Junior Writing Portfolios, containing FYC research papers and engineering lab reports, was chosen for analysis in five broad rhetorical categories including invention, disciplinary knowledge, audience awareness, arrangement, and style. Informed by Yancey, Roberston, and Taczack's 2014 study of writing transfer in composition courses, we grouped 17 engineering writing samples into three types of prior knowledge as identified in their study: remix, assemblage, and critical incidents. We found that the remix group students (n = 9) demonstrated an ability to integrate new engineering disciplinary knowledge into the schema of the old FYC knowledge. We observed a mixture of productive and unproductive transfer from FYC courses to engineering major courses with the assemblage group (n = 3). The critical incident students (n=5) struggled with multiple aspects of rhetorical principles, and they received the lowest scores in audience awareness and arrangement. Results from an accompanying focus group comprised of engineering students reported their perceptions of the similarities and distinctions between FYC assignments and engineering lab reports. These combined results suggest that students developed an understanding that genre features are genre specific and informed by disciplinary contexts.