Recently, an interest has developed in the use of whole green grains as functional food materials. The present study was conducted to provide the baseline data for the stable production of whole green grains in 20 cultivars of wheat by investigating the greenness of grain with maturation (from 20 th to 41 st day after heading, at an interval of 3 days). On the 20 th day after heading, the grains were dark green with a wrinkled long-oval shape. After the 35 th day of heading, the grains turned almost yellow with an oval shape. Their redness (‘a’ value of chromaticity) increased from the 20 th to 41 st days after heading, indicating a negative value up to the 32 nd day after heading. A significant decrease in their chlorophyll content was observed with maturation. The yield of whole green wheat grain (including greenish yellow grain) was the highest from the 32 nd to 35 th after heading. Therefore, we concluded that the optimal harvesting period for whole green wheat grain was from the 32 nd to 35 th day after heading. The heading time of various cultivars ranged from April 28 to May 5, the time of Jopummil cultivar grew the fastest among them, such as Gurumil, Alchanmil, but Dahongmil got the latest in heading time. The greenness of seven cultivars (Jeokjungmil, Keumkangmil, Jogyeongmil, Jopummil, Baekjungmil, Yeonbaekmil, and Milseongmil) was relatively higher than that of the others. The yield of greenish whole grain was relatively high in six cultivars (Alchanmil, Baekjungmil, Eunpamil, Yeonbaekmil, Dahongmil, and Urimil). Based on their greenness and yield, the Baekjungmil and Yeonbaekmil cultivars have been considered to be optimal for the production of whole green wheat grain.