Forage quality determines livestock production and overgrazing results in significant changes in forage quality of rangeland species. This study aimed to compare the effects of overgrazing on forage quality of Artemisia sieberi, Zygophyllum eurypterum and Stipa barbata as dominant species producing more than 90% of livestock feed in arid rangelands of Semnan, Iran. The study area was classified into non-grazed and overgrazed sites based on the estimated carrying capacity. Data collection was conducted at the end of the grazing season. The collected forage samples were analysed for crude protein (CP), potassium (K), phosphorus (P), acid detergent fibre (ADF), digestibility, percentage of dry matter digestibility (DMD) and metabolic energy (ME). Results from the t-test indicated that overgrazing led to significant (p < 0.05) reduction in CP, K, P, DMD and ME and a significant (p < 0.05) increase in ADF in A. sieberi and Z. eurypterum, in comparison to plants from non-grazed areas, with CP being the most sensitive qualitative parameter to overgrazing in the two species. Shrubs including A. sieberi and Z. eurypterum showed more susceptibility to overgrazing while the grass species S. barbata
