This study aimed to determine the efficacy of a content acquisition and reading comprehension treatment implemented by eighth-grade social studies teachers. Using a within-teacher design, the eighth-grade teachers' social studies classes were randomly assigned to treatment or comparison conditions. Teachers (n = 5) taught the same instructional content to both treatment and comparison classes, but the treatment classes used instructional practices focused on teaching essential words, text as a source for reading and discussion, and team-based learning approaches. Students in the treatment conditions (n = 261) scored statistically higher than students in the comparison conditions (n = 158) on all three outcomes: content acquisition (ES = 0.17), content reading comprehension (ES = 0.29), and standardized reading comprehension (ES = 0.20). Findings are interpreted as demonstrating support for the treatment in improving both knowledge acquisition and reading comprehension within content area instruction. (Contains 8 tables, 1 figure, and 1 note.)