Abstract Integrated writing tasks that depend on input from other language abilities are gaining ground in teaching and assessment of L2 writing. Understanding how raters assign scores to integrated tasks is a necessary step for interpreting performance from this assessment method. The current study investigates how raters approach reading-to-write tasks, how they react to source use, the challenges they face, and the features influencing their scoring decisions. To address these issues, the study employed an inductive analysis of interviews and think-aloud data obtained from two raters. The results of the study showed raters attending to judgment strategies more than interpretation behaviors. In addition, the results found raters attending to a number of issues specifically related to source use: (a) locating source information, (b) citation mechanics, and (c) quality of source use. Furthermore, the analysis revealed a number of challenges faced by raters when working on integrated tasks. While raters focused on surface source use features at lower levels, they shifted their attention to more sophisticated issues at advanced levels. These results demonstrate the complex nature of integrated tasks and stress the need for writing professionals to consider the scoring and rating of these tasks carefully.