This study was carried out to find out the effect of cool-season turfgrass overseeding onto zoysiagrass(Zoysia japonica L.) for extending green color and solving traffic problem during dormant periods. Overseeding rates of cool-season turfgrasses were $10g/m^2$ of Kentucky bluegrass(KB1), $20g/m^2$of Kentucky b1uegrass(KB2), $60g/m^2$ of perennial ryegrass(PR), $80g/m^2$ of Tall fescue(TF), and $10g/m^2$ of Kentucky bluegrass + $10g/m^2$ of perennial ryegrass mixture(KB+PR) onto 2m${ imes}$2m(width${ imes}$length) zoysiagrass plots with 3 replications.1 to 9-sca1e of visual quality and visual color were measured after treatment, Consequently cool-season turfgrass overseeding gave a good performances of extending the green periods and enhancing the turf grass quality. KB1 and KB2 were found to be excellent performances for visual quality and visual color compared to PR, TF, KB+PR and control. KB2 showed better turf performances than KB1 within Kentucky bluegrass overseedings. Turfgrass color was kept up for 10 months by overseeding of cool-season turfgrasses(KB1, KB2, PR, TP, KB+PR) compared to about 5~6 months by zoysiagrass(Control). The visual quality and visual color of PR and TF showed good performances during a green-up period of spring, but decreasing tendencies through the summer.Percent diseases data revealed also higher ratings for PR and TF compared to for KB1 and KB2.