Historically, research has identified the optimum period of seeding Canadian Western Red Spring (CWRS) wheat in the Brown soil zone to be between late April and mid-May, and approximately mid-May in the Dark Brown soil zone. The recent development and release of new spring wheat cultivars with significantly different genetic makeup (Canada Prairie Spring (CPS) wheats) prompted this study to determine if the established criteria were valid for them. Seeding date experiments involving one CWRS wheat (Neepawa) and three CPS wheats (HY320, HY355, HY912) were carried out at Swift Current (1984–1988) and at Regina and Scott (1985–1988). Although significant seeding date × cultivar interactions occurred for several of the characteristics measured (e.g., yield, protein concentration), no cultivar consistently responded differently than the others. However, the difference in days to reach maturity between the later maturing CPS cultivars and the CWRS cultivar, Neepawa, generally increased with delayed seeding making the CPS cultivars more susceptible to early fall frost damage which could decrease their yields and grain quality. Our results showed no reason to change recommendations for seeding dates in either soil zone, and both types of wheat can be treated similarly except that late seeding for CPS wheats should be avoided.Key words: Seeding date, grain yield, GDD, protein, wheat