Market forces provide a foundation for the expectations of efficiency in contracting out. However, often the lack of competition in particular industries creates powerful companies that are able to negotiate contracts in their favor, reducing improved performance for government agencies. To study how market power influences performance in service delivery in the transit industry, we examine individual contracts as our unit of analysis. We hypothesize that a vendor’s market power directly influences an individual contract’s operational efficiency. We find that the lack of competition in the execution of contracts is an important determinant of agency performance.