At ground level, the air pollutant ozone (O₃) damages wheat yield and quality. We modified the DO₃SE-Crop model to simulate O₃ effects on wheat quality and identified onset of leaf death as the key process affecting wheat quality upon O₃ exposure. This aligns with expectations, as the onset of leaf death aids nutrient transfer from leaves to grains. Breeders should prioritize wheat varieties resistant to protein loss from delayed leaf death, to maintain yield and quality under O₃ exposure.