Source-based essays are evaluated both on the quality of the writing and the content appropriate interpretation and use of source material. Hence, composing a high-quality source-based essay (an essay written based on source material) relies on skills related to both reading (the sources) and writing (the essay) skills. As such, source-based writing must involve language comprehension and production processes. The purpose of the current study is to examine the impact of reading, writing, and blended (i.e., reading and writing) strategy training on students’ performance on a content-specific source-based essay writing task. In contrast to general source-based writing tasks, content-specific source-based writing tasks are tasks wherein writers are provided the source material on which to base their essays. Undergraduate students (n = 175) were provided with strategy instruction and practice in the context of two intelligent tutoring systems, Writing Pal and Interactive Strategy Training for Active Reading and Thinking (iSTART). Results indicated that participants in the blended strategy training condition produced higher quality source-based essays than participants in the reading comprehension-only, writing-only, or control condition, with no differences observed between the latter three conditions. Further, the benefits of this blended strategy instruction remained significant regardless of prior reading and writing skills, or time on task.