Aim: The effects of feeding with different plants on some biochemical parameters in free-range broiler farming were investigated. Materials and Methods: Hubbard Isa Red-JA broiler chicks were used: The 1st group (control) was fed ad libitum with consantrated feed in closed cages. The 2nd group was fed with Medicago sativa L, the 3rd group with Bromus inermis Leyss and the 4th group with 50% alfalfa+50% bromegrass cultivated areas, by means of mobile cages. Thymus vulgaris L. was cultivated among all groups. On the 42nd and 84th days, blood samples were taken from 8 of the chicks in each main group (totally 64 animals). Serum iron, magnesium, total lipid, urea, uric acid, creatinine, total bilirubin, direct bilirubin concentrations, and gamma glutamyl transferase, lactate dehydrogenase and creatin kinase activities were determined. Results: Iron concentrations increased in the 2nd and 3rd groups on the 42th day and in the 2nd and 4th groups on the 84th day, compared to control (p < 0.05). Magnesium concentrations were higher in the 2nd, 3rd, and 4th groups, compared to control, on the 42nd day (p < 0.05). Total lipid concentrations were higher in the 3rd and 4th groups on the 42nd day, while lower in the 2nd group on the 84th day, compared to control (p < 0.05). Uric acid concentrations decreased on the 84th day in the 2nd, 3rd and 4th groups, compared to control (p < 0.05). Conclusion: It is suggested to feed broilers in free-range system with Medicago sativa L, Bromus inermis Leyss and Thymus vulgaris L.