Barium Strontium Titanate (Ba0.5Sr0.5TiO3) thin films on (100) oriented MgO substrates were deposited by Pulsed Laser Deposition (PLD) technique. The deposition temperature of 750 degrees C is kept constant and the oxygen working pressure is varied from -1 x 10(-1) mbar to 1 x 10(-4) mbar. The X-ray diffraction pattern shows that higher oxygen working pressure deposited films are partially crystalline. The lower oxygen working pressure (1 x 10(-4) mbar) deposited films showed improved crystallinity. The crystallinity is further increased with a particular orientation as the laser fluence increased from lA J/cm(2) to 2 J/cm(2).The microwave dielectric properties of these films were measured using Inter Digitated Capacitor (IDC) test structure. It is found that the maximum tun ability (in IDC configuration) of 16.5% at 1GHz is obtained for oxygen working pressure and high fluence (1 x 10(-4) mbar and 2 J/cm(2)) deposited films, whereas the other films tunabilities are in the range of 1-2% only. These studies also help us to explore the correlation between structure and microwave dielectric properties. Hence, in the present study the 1 x 10(-4) mbar and 2 J/cm(2) deposition conditions are found to be more helpful in unleashing conditions that lead to better tunability in Ba0.5Sr0.5TiO3 films. (C) 2017 Elsevier B.V. All rights reserved.