Purpose and Method of Study: This study focused on the relationship between the cost of undergraduate education (COUE) and graduation rates in four-year institutions in Oklahoma. The purpose of this study was to examine the relationship between the cost of undergraduate education (COUE) and graduation rates at four-year higher education institutions in Oklahoma using the IPEDS 150% graduation rate, enrollment, and financial aid datasets. The study utilized an ex post facto quantitative design and collected data on 26 public and private not-for-profit four-year higher education institutions in Oklahoma from the Integrated Postsecondary Education Data System. A two-block hierarchical regression was applied to analyze the data, supported by principal component analysis and Horn's parallel analysis. Findings and Conclusions: For public higher education institutions, Model 1 explained 76% of the variance in graduation rates across the years. Adding F1 Expensiveness to the model only increased by 2%, which was significant at ?R² 2%. Other factors affecting graduation rates for public institutions were the share of full-time, first-time students; use of financial aid (positive); and Pell Grants and other sources of grants (negative). For private not-for-profit higher education institutions, COUE was not evident in the relationship with graduation rates. Model 1 explained 67% of the variance in graduation rates. However, the use of financial aid, institution size, students awarded Pell Grant (positive), and use of loans (negative) were found to influence the graduation rates. When considering the whole sample, the cost of education positively correlated with graduation rates but did not affect their variance significantly. Other factors were financial aid, institution size, institutional grant (positive), use of loans, and median household income (negative). The results and conclusions recommend that policymakers direct their efforts to improve the accessibility of financial aid, reducing the share of students financing their education through loans and providing more support to students who experience financial difficulties. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]