Currently and in the past, college access and admissions has been an important topic in higher education, regardless of national and historical background. It is also one of the essential mechanisms that determines the organizational rise and fall of postsecondary institutions as a social system. Utilizing a comprehensive literature review and theoretical background that includes sociology, economic, and policy and administrative perspectives, this dissertation comprises two studies. Specifically, the first study examines the implementation of early admissions (Early Action/Early Decision) to explore the values and messages behind such policies, utilizing text data and qualitative research method, a content analysis, in four-year colleges and universities in the U.S. Following that, the second study investigates the consequences of early admissions policies on institutional outcomes using a national large panel dataset from 2004-2018 and the causal modeling of a quantitative research method, a difference-in-differences design with two-way fixed effects model, in four-year institutions in the U.S. Both studies are illuminated through the triangular conceptual framework of this dissertation: diversity, quality, and affordability. The individual studies respectively address the study’s purpose, research questions, research design and method, results and limitations, and provide rich discussion on the three aspects of diversity, quality, and affordability in admissions, and future study and practices are suggested. Additionally, further discussions, implications, and suggestions for policy and practice based on the findings from the two studies are discussed in the last chapter. This research aims to expand our understanding of early admissions policies and serve as a steppingstone to further develop college admissions and access policies and practices in higher education.