The studies were conducted at Transitional Zone Agricultural Research Institute in Eskisehir and Selçuk University in 2008-2010 growing seasons. Two bread wheat cultivars (Gerek 79 and Bezostaja 1) were used as plant material. Experimental treatments were 0, 30, 60, 90 and 120 kg N ha-1 applied at planting and tillering stages (early-season treatments) and 0, 20, 40 and 60 kg N ha-1 (urea form) applied at heading stage (late-season treatments) as foliar applications. A variation was created in terms of SPAD and TN at heading stage through different nitrogen rates in traditional nitrogen application time. Results under rain-fed conditions revealed that foliar nitrogen at heading stage could increase the protein content at least 1%, and the critical threshold NSPAD value was 0.96 for Bezostaja 1 and 0.94 for Gerek 79. On the other hand, the threshold TN value was 4.22% for Bezostaja 1 and 3.75% for Gerek 79 under the same conditions. The increase in grain protein content of Bezostaja 1 per 10 kg ha-1 of N was 2.0% in early-season and 3.2% in late-season treatments. The same increase rates for Gerek 79 were 1.5% in early-season and 2.7% in late-season treatments. Although both early and late-season treatments were effective on protein content and related quality traits, the application of foliar solution in heading stage was more dominant as compared to the traditional nitrogen application time.