Nitrogen and water interact in diverse ways affecting crop production, and the concept of co-limitation provides a quantitative framework for integration. We tested the hypothesis that selection for yield increased the water-N colimitation in wheat adapted to winter-rainfall environments of Australia. To evaluate the hypothesis we measured yield and traits, N uptake and water use in two historic collections of cultivars released between 1958 and 2007, and between 1969 and 2015. Crops were grown under nine environmental conditions resulting from the combination of sites, seasons, and water and N availability. Genetic gain of yield averaged 20.2 kg ha-1 year-1 and was associated with a linear increase in N-water co-limitation. Furthermore, yield improvement was associated with an increase in N uptake per mm of evapotranspiration at a rate of 0.0019 kg N mm-1 year-1. Our findings support the critical role of nitrogen for the adaptation of wheat to low rainfall environments, and suggest opportunities to improve grain yield based on traits that integrate resources.