We examined classrooms as complex systems that affect students' literacy learning through interacting effects of content and amount of time individual students spent in literacy instruction along with the global quality of the classroom learning environment. We observed 27 3rd-grade classrooms serving 315 target students using 2 different observation systems. The first assessed instruction at a more micro level, specifically, the amount of time individual students spent in literacy instruction defined by the type of instruction, role of the teacher, and content. The second assessed the quality of the classroom learning environment at a more macro level, focusing on classroom organization, teacher responsiveness, and support for vocabulary and language. Results revealed that both global quality of the classroom learning environment and time individual students spent in specific types of literacy instruction covering specific content interacted to predict students' comprehension and vocabulary gains, whereas neither system alone did. These findings support a dynamic systems model of how individual children learn in the context of classroom literacy instruction and the classroom learning environment, which can help to improve observations systems, advance research, elevate teacher evaluation and professional development, and enhance student achievement.