Between 1946 and 1975, Industrial Organization research coalesced around the link between market structure and competitive outcomes, emphasizing industry configuration, barriers to entry, and the regulatory environment. Researchers combined empirical analysis with formal models to examine how firm organization and strategy influence performance, often through the lens of multidivisional and decentralized designs. Methodological emphasis on cross-sectional and longitudinal data anchored policy-oriented inquiries into regulation, competition, and market power, while maintaining a foundation of descriptive and case-based studies that identified robust patterns of rivalry and welfare effects.