This study explored the content-based literacy instruction of English language learners (ELLs) across multiple classroom settings in U.S. elementary schools. The following research questions guided the study: (a) How are ELLs taught English in two types of instructional settings: regular content-area literacy instruction in the all-English classroom and content-based ESL instruction in the ESL classroom? (b) How does each ELL student respond to these two types of instruction? How does the student participate in each classroom setting, and what attitudes does he or she have toward that classroom setting? (c) What factors influence the students' responses, participation, and attitudes within the two types of instructional settings, and how? In this research, the main conceptual framework was a sociocultural theoretical framework, with a focus on Vygotsky's social constructivism and Lave and Wenger's community of practice. This study used qualitative research methodology to explore in depth the nature of the teachers' approaches, the students' learning, and general background factors as a whole. Data were collected in 11 classrooms at two elementary schools by using three methods: classroom observations, teacher and student interviews, and written materials. Data were analyzed using within-case analysis and the constant comparative method. For the main findings, first, the results revealed this study was a realistic investigation of how the ELLs were taught English through the content areas, based on an examination of the teachers' perspectives on content-based ESL instruction or regular content-area literacy instruction, the classroom structures involving group work, and the teachers' instructional approaches in each instructional setting. Next, the results of the study revealed that the students' interactions and participation differed based on the types of instruction used in the all-English classroom. However, in the ESL classroom the students were generally active and took a large part in all types of grouping arrangements. Last, the results of this study revealed a triangle of influential factors affecting the students' learning and participation through content-based instruction in the two classroom settings. The students themselves were in the middle of the triangle, as the main avenue for their own learning, and at the vertices were three other elements: school contexts, family backgrounds, and additional factors. In the end, this study suggests how educators, researchers, and policy makers inside and outside the United States might apply the findings of the study to various educational situations to develop an appreciation for content-based instruction and promote ELLs' understanding. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]