With respect to European growth conditions very little information is available on how future atmospheric CO ₂ concentrations [CO ₂] might affect quality characteristics of important crops. Winter wheat cv. 'Batis' and winter barley cv. 'Theresa' were grown for two growing seasons each under ambient [CO ₂] (ca. 375 μmol mol ^-1) and elevated [CO ₂] (550 μmol mol ^-1) with two different nitrogen (N) fertilization levels (adequate N supply / ca. 50% of adequate N) in the course of a six year crop rotation. Effects on grain quality and grain elemental composition were investigated. Grain crude protein concentrations were lowered under elevated [CO ₂] by -4% to -13% in wheat and by -11% to -13% in barley. Reduced N supply decreased crude protein concentrations in wheat and barley by -14% to -22% and by -12% to -19%, respectively. In both species, starch concentration was increased by +4% on average due to reduced N fertilization. In wheat, both CO ₂ enrichment and low N supply reduced the activity of total and soluble β-amylase (-11% and -7%), Hagberg falling number (-7%), and single kernel hardness (-18%). In barley, both of the treatments induced reductions in the viscosity of the water extract (-25% on average). Concerning minerals, sulphur concentrations were depleted under both elevated [CO ₂] and low N supply by averages of -5% in wheat and -14% in barley. Reduced N supply caused -8% lower means of wheat grain calcium concentrations and reduced zinc concentrations on average by -23%. According to these results, flour from cereal grains grown under elevated [CO ₂] and/or low N fertilization will have a diminished nutritional and processing quality and an altered elemental composition.