Abstract: Background and Objectives: The forage grasses shows considerable variations in yield, morphological characteristics and feeding value at grazed, ungrazed and different ecological conditions. For this reason, these characters of the same species should be known under different ecological conditions. The aim of the present investigation was to determine the some forage quality traits six dominant cool-season forage grasses grown as naturally in the protected forest range at northern Bulgaria ecological conditions. Materials and Methods: Samples were collected (approximately 450 g biomass) for two years at full bloom stage, which were chosen not damaged by biotic and abiotic factors. Whole plant samples were sterilized with 2% sodium hypochlorite for 15 min and washed distilled water three times. Potassium (%), phosphorus (%), calcium (%), magnesium (%), crude protein (%), acid detergent fiber (%) and neutral detergent fiber (%) were determined in these dried (at 55̊C for 48 h) samples. The crude protein content dry matter (%) was determined by the micro-Kjeldahl method. All samples were analyzed in triplicate. Results: The highest crude protein (14.23%), calcium (3.88%), potassium (3.22%) ratios were determined in smooth brome, whereas the lowest phosphorus ratio (0.22%) was found in same plant. Sheep fescue produced more ADF (33.78%) and NDF (62.10%) ratios than other species. The magnesium ratio ranged from 0.26-0.28%. The mineral contents of those are generally adequate to meet the needs of livestock. Conclusion: Therefore, sheep fescue, red fescue, perennial ryegrass, Kentucky bluegrass, orchardgrass and smooth brome can be grazed to obtain mineral, fiber and crude protein contents in similar ecological conditions of the world.