The reading of complex text has become part of the reading curriculum since the introduction of the Common Core State Standards. However, little research has been conducted to determine the effect of complex text instruction on comprehension and fluency in secondary readers. This study randomly assigned 53 11th-grade US history students to one of two classroom conditions. In one classroom, students were taught using a business-as-usual approach while the treatment classroom taught students to use text annotation and writing to improve their understanding of complex texts over a 24-week period. Students were pre- and post-tested using a standardized reading comprehension assessment and curriculum-based measurement fluency measures. Results revealed statistically significant improvement favoring the treatment group for both reading comprehension and fluency. Results and implications for instruction are discussed.