This study investigates the relationship between geographic market size and firms’ competitiveness in bidding for public procurement, focusing on their ability to submit lower bids. Using a natural experiment design, the analysis first controls for firm size and other characteristics, showing that firms operating in larger geographic areas are more likely to bid competitively at lower prices compared to firms limited to smaller regions. Causality is then tested through an exogenous event, confirming that wider geographic scope itself generates a competitive advantage rather than being a mere outcome of competitiveness. The findings highlight the importance of networks and regional breadth, particularly in industries such as construction, where operating across wider areas enhances firms’ efficiency and cost competitiveness. From a practical perspective, the study suggests that firms seeking to strengthen their bidding competitiveness should strategically expand their operational scope. At the policy level, the results imply that encouraging firms to engage across larger markets may foster more competitive procurement outcomes. The study’s originality lies in defining competitiveness as the ability to bid at lower prices in public tenders and demonstrating that broader market activity causally contributes to such competitiveness, thereby offering new insights into the design of procurement and regional economic policy.