Genetic gains in quality traits were assessed in grain samples from 4 field experiments involving 16 bread wheat varieties representative of those most widely cultivated in Spain during the 20th century. The allelic composition at three glutenin loci (Glu-A1, Glu-B1, and Glu-D1) was obtained by PCR-based DNA markers and published references. From 1930 to 2000 grain protein content decreased by −0.030%y−1, or in relative terms by −0.21%y−1, but the protein produced per hectare increased by 0.39%y−1. Alveographic tests revealed significant changes in dough rheological properties. Dough strength (W) and tenacity (P) increased at relative rates of 1.38%y−1 and 0.99%y−1, respectively, while dough extensibility (L) decreased by −0.46%y−1, resulting in an increase of 1.45%y−1in dough equilibrium (P/L). The rise in protein quality could be related to the replacement of the null allele by subunits 1 or 2* at Glu-A1 and the prevalence of subunits 7+8 and 5+10 at Glu-B1 and Glu-D1 loci, respectively, in the most recent varieties. Dough extensibility was affected by water input during the crop cycle, this relationship being partially explained by the presence of the 5+10 HMW glutenin subunit. Fermentation tolerance was improved in the most modern varieties. Collapse during fermentation was avoided only in doughs with a W≥159 J×10−4 and a P/L≥0.56mm H2O mm−1, levels achieved by most of the modern varieties. The over-strong and unbalanced rheological properties of some modern varieties resulted in highly porous doughs, and no clear advances in dough maximum height during fermentation were attained.