This research was conducted to determine forage yield, chemical composition, milk yield and milk composition in dairy cattle grazing on pasture established with species and mixtures of Perennial ryegrass (Lolium perenne, Bastion,PR), Orchardgrass(Dactylis glometata, Pizza,OG) and White clover(Trifolium repens, Huia,WC). In this research conducted for two years, the grazing experiment was carried out according to a change over trial design. For this purpose, a total of 6 Holstein Friesian cows (at the 2nd lactation and with an average of 520 ± 26 kg live weight) were used for two periods, each of which consisted of 30 days (8 days of adaptation and 22 days of the basis period). The milk nutritional composition of the animals (dry matter, fat and protein content) was determined in the last three days in the last five consecutive days of each lactation period. The acid detergent fiber (ADF) content of pasture obtained from Perennial ryegrass + White clover mixture (PRWC) was found to be lower than that obtained from the other two (PR and OG) pasture and Net Energy Lactation (NEL) content was found higher in the first grazing period in the first year. However, the effect of the investigated pastures on milk yield was not significant, but it was found that the effects on milk protein yield in the first year and dry matter of milk in the second year were significant. In the first year of grazing period, milk yield, milk fat yield and protein yield were found to be significant. The results of this study showed that under these operating conditions, the botanical composition of the pasture had no effect on the amount and composition of the milk, but the milk yield decreased as the vegetation period advanced.