Thin films based on quaternary compounds such as Cu (lnGa) Se2 (CIGS) find application in photovoltaics technology as absorber layers. The addition of Ga to the usual CulnSe2 material makes it more suitable due to higher band gap value, which has better matching with solar spectrum. In the current work, we have deposited individual elements of the compound sequentially, using a resistive heating method. These films are structurally characterised by x-ray Diffraction technique. A high temperature attachment in the XRD machine (Rigaku MAX-IIA) is used to investigate the phase variations in these thin films in the temperature range 150-1250 oC. In this paper, results of these phase studies along with the preferred orientation and grain size dependence on temperature are presented.