Understanding the changes in grain quality and its response to nitrogen (N) fertilizer during the improvement of crop varieties has great significance in both crop breeding and cultivation. This study aimed to investigate the changes in grain yield and quality during the improvement of mid-season indica rice varieties and the effect of N fertilizer application on the quality. Twelve representative mid-season indica rice varieties (including hybrid combinations) grown in Jiangsu Province during the last 70 years were used with three N application treatments: 0 kg N ha–1 (zero N, 0N), 210 kg N ha–1 (medium amount of N, MN), and 300 kg N ha–1 (high amount of N, HN). These varieties were divided into four groups, including 1940-1950s, 1960-1970s, 1980-1990s, and 2000-2010s (super rice), according to their application times. With the variety improvement, grain yield was significantly increased, and the head rice percentage, chalkiness, ratio of length to width, amylose content, gel consistency, protein components, and rapid viscosity analyzer (RVA) pasting properties were all significantly improved. However, chalkiness for modern varieties was still high. Grain yield was the highest in HN for super rice varieties, and in MN, for other varieties or no significant difference between MN and HN. With the increase in N application, protein content and chalkiness increased, taste quality decreased which was evidenced by the reduction in breakdown values and the increase in setback values. The contents of K, P, S, Ca, and Mg in the head rice decreased in HN compared with those in 0N or MN. The results demonstrate that the improvement of mid-season indica rice varieties markedly improves both grain yield and quality. Generally, increasing N fertilizer application especially up to the HN level could decrease rice quality. How to increase both grain yield and quality through optimizing N management is still a question to be studied.