Assessment of writing and design are active areas of research in engineering education, as are issues of retention and transfer of learning. A variety of methodologies have been applied to these questions, including surveys directed to measuring design skills and rubrics describing desired textual features. Retention and transfer of learning research generally focuses on evaluating strategies for reinforcing or augmenting writing instruction in advanced engineering courses, which usually involve explicit emphasis on organization, grammar, style, and clarity. More progressive approaches recognize the rhetorical complexity of engineering writing and encompass matters of content as well. Writing in design courses has been of particular interest in this regard. The present study focuses on a junior/senior level design course. Rubrics to evaluate experimental research reports and final design reports from this course were developed. The rubrics are based on assignments and rubrics from earlier courses where students initially receive instruction and practice in experimental and design projects and the associated reports. The rubric indicators address typical elements of reports, such as adherence to format and style conventions, but also capture rhetorical strategies associated with design thinking. The presentation of this work will describe the writing assessment methodology and preliminary results.