The effects of the thermal processing and iron doping on RF magnetron co-sputtered barium strontium titanate thin film properties have been investigated. X-ray diffraction and Raman spectroscopy have been used to determine the structural evolution of the films as a function of the annealing temperature and the amount of iron dopant. X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy were employed to gain information about the chemical binding states and the defect structure. The enhancement of the quality factor Q, as well as the decreasing permittivity and tunability due to iron acceptor doping are demonstrated.