Due in large part to their open access and affordability, community colleges have long played a central role in providing students with immigrant backgrounds who are English language learners (ELLs) with access to postsecondary education. Researchers have noted that English as a second language (ESL) courses have been the primary form of support provided by institutions to foster the college persistence and success of ELLs. Nevertheless, despite their importance, little is known about the extent to which participants who engage in postsecondary ESL programs are likely to succeed in college. Therefore, the purpose of this study is to analyze quantitative administrative data and use qualitative data to examine how ELLs seeking postsecondary education acquire the knowledge, skills, and abilities they need to be successful in college programs. It does so by exploring the role of two ESL pathways at a Large Urban Community College System (LUCCS): (1) the English Language Immersion Program (ELIP) and (2) the traditional ESL sequence. In the quantitative phase of the study, I use a propensity score matching approach together with a large administrative dataset to examine the effects of ESL pathways on ELLs college English enrollment and performance, credit accumulation, and college progression and degree outcomes. I find no evidence that participation in ELIP versus traditional ESL leads to significant impacts on college English enrollment and performance within three and five years. I also find consistent evidence that students who participate in ELIP versus traditional ESL earn fewer college level credits, but they also earn significantly fewer equated credits over three and five years--suggesting they spend less time on remedial coursework. Results also indicate that ELIP participants are more likely to persist and less likely to drop out, but there is no effect on graduation and/or transfer within three and five years. Finally, results indicate that males, younger students (age 23 and younger), and foreign-born, U.S. educated (generation 1.5) students experience less negative impacts on college credits and more positive impacts on several of the longer term outcomes. Next, qualitative methods were used to help explain the quantitative results. In particular, interviews and focus groups were conducted to explore with program instructors, staff, and students' their perceptions of their engagement in ELIP and traditional ESL and its respective role in students' success in college programs. Findings suggest that null impacts on college English enrollment and performance could be explained by the finding that both ESL pathways emphasize the acquisition similar skills and employ parallel instructional approaches to help students acquire these skills. Findings also suggest that negative impacts on college credit completion may be due to the programs' respective college enrollment experience. The structure and length of the traditional ESL sequence helps explain negative results for equated credits. Differences in persistence and drop out as well as differences for subgroups are found to be partially explained by the activities and interactions that are fostered by a high intensity program. This study provides suggestive evidence that the ESL pathway taken by degree-seeking students at LUCCS has important implications for their college outcomes. It also suggests that there exist heterogeneous impacts by gender, age, and immigrant status. ESL program staff and college administrators can use these findings to explore strategies that will better support ELL student success. [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.]