Early reformers reasoned that by changing institutional structure in local government you could solve organizational problems. Institutional structural reform in local government has interested scholars ever since. The reform movement in the early 20th century firmly established the council-manager (administrative) model of government, which along with the mayor-council (political) model, is now utilized in 92% of all U.S. municipalities. Recent scholars have observed and reported on the fact that, increasingly, mayor-council municipalities are adopting structural changes that resemble characteristics found in council-manager municipalities and vice-versa. This research seeks to examine the question of whether these structural changes have any effect on these local governments by examining the behavior of Chief Administrative Officer’s (CAO) and municipal outputs. The author examines a representative sample of 266 administrative and political municipalities within the U.S. having a population between 10,000 and 250,000. The institutional structures of these 266 municipalities are measured for political model and administrative model characteristics using three separate independent variables. The effects of institutional structural change is measured using group mean T-tests, ANOVA analysis, and multiple regression for per capita expenditures, working time allocation between the management, policy, and political role activities for the CAO, the quality of services provided, and the involvement level of the CAO compared to the council in the mission, policy, administrative, and management dimensions of municipal responsibilities. The study findings are mixed; significant effects are found in some but not all variables. Changing local government structures from characteristics found in the political model to characteristics found in the administrative model: makes no difference in municipal expenditures; makes a difference in how a CAO allocates his time in management and political activities but not policy activities; makes a difference in how the CAO perceives quality of services; makes a difference in the level of involvement for the CAO in the policy, administrative, and management dimensions of responsibility but not the mission dimension. Overall, this study has found that, by using more complex methods to measure institutional structure change, changes in institutional structures do make a difference in important areas of CAO behavior and outputs in local governments.