One strength of educational games stems from their potential to increase students' motivation and engagement during educational tasks. However, game features may also detract from principle learning goals and interfere with students' ability to master the target material. To assess the potential impact of game-based learning environments, in this study we examined motivation and learning for 84 high-school students across eight 1-hr sessions comparing 2 versions of a reading strategy tutoring system, an intelligent tutoring system (iSTART) and its game-based version (iSTART-ME). The results demonstrate equivalent target task performance (i.e., learning) across environments at pretest, posttest, and retention, but significantly higher levels of enjoyment and motivation for the game-based system. Analyses of performance across sessions reveal an initial decrease in performance followed by improvement within the game-based training condition. These results suggest possible constraints and benefits of game-based training, including time-scale effects. The findings from this study offer a potential explanation for some of the mixed findings within the literature and support the integration of game-based features within intelligent tutoring environments that require long-term interactions for students to develop skill mastery.