We have fabricated La0.7Ba0.3MnO3 (LBMO) thin films by a pulsed laser deposition technique using a low partial pressure (10-2 mbar) of O2+5% O3. In order to study the role of oxygen content in the transport properties, the temperature dependence of the resistivity has been measured as a function of the temperature and the time of a post-annealing process. Strain-less LBMO thin films deposited on SrTiO3 substrates show a metal insulator transitions temperature TMI≃345 K (equal to that found in bulk material). A T2.5-power law has been measured in R(T) at low temperature, supporting the disorder-induced single magnon scattering scenario. At high temperature (T≫TMI) an activated behavior characteristic of polaronic carriers has been measured. Magnetotransport properties show a metal-like behavior and a negative magnetoresistance (MR) in the whole temperature range. With an external magnetic field of 70 kOe, the MR reaches the maximum value of 170% at about 320 K.