The effect of substrate temperature on the crystallographic texture and surface morphology of Ba0.5Sr0.5TiO3 deposited by rf magnetron sputtering on (111) oriented Pt (150 nm)/Ti (10 nm)/SiO2 (300 nm)/Si (100) substrates is reported. The onset of crystallinity is observed above 500 °C, beyond which all films are oriented along the (111) plane up to a temperature of 800 °C. Over this temperature range, the misfit strain and root mean square roughness (rmsroughness) peak at 600 °C, decreasing beyond this peak value. The tunability of the dielectric constant at 100 kHz is highest (60% for a field strength of 300 kV/cm) at the lowest values of rmsroughness and misfit strain and decreases as these values increase. It is also shown that the morphology of the Pt underlayers is strongly affected by the processing conditions. This in turn influences the tunable behavior of the BST films as much as the substrate temperature during growth and the consequent microstructural variations.