Appropriate utilization of rangelands leads to vegetation stability and reduction of risk of range degradation. Determining allowable utilization of range plant species is required to calculate grazing capacity of rangelands. To achieve this goal, forage production and vigor of FESTUCA OVINA was studied in Qarebagh rangelands of western Azarbayjan Province. Treatments included four harvested intensities (25, 50 and 75 percent of total above ground biomass) and control (no harvest). A split plot over time design was used over four years (1386-1389) using SAS and IRRISTAT software. The results showed that forage production and vitality of F. OVINA was significantly different between years of study and different harvesting intensities. No significant differences were detected between control treatment and 25% harvest and also between25 and 50 percent harvest intensities. With increasing harvesting intensity to 75 percent, production and vitality of the species were significantly decreased. Overall vigor of the species have decreased during 1386 to 1389. According to AMMI analysis, the first interaction principal component (IPC1) had a significant effect and expressed 98.6 percent of the interaction of the sum of squares. The first main component biplot interaction showed that the 75 percent treatment had lowest production and stability, and 50 percent treatment had the highest stability. To maintain the plant health and vigor, 50 percent treatment can be recommended as appropriate harvesting intensity for F. OVINA.