Many students struggle with gaining knowledge and writing about content text material and therefore require effective intervention. In a randomized controlled trial study, 77 low-achieving fourth-grade students received reading comprehension instruction or reading comprehension plus writing instruction or were assigned to a no-treatment control. Knowledge outcomes were evaluated through students' retelling and performance on a standardized reading test. Written language-based outcomes were analyzed using a computer software program for semantic and syntactic measures. Analyses indicated that students in reading comprehension instruction and reading comprehension plus writing instruction outperformed the control group on oral and written retelling, a standardized reading test, and semantic measures. Syntactic measures, however, did not show statistically significant differences by treatment or control group. Implications for including language instruction and assessments within multi-component instruction are suggested.