Reducing the operating voltage and processing temperature are the crucial factors in the progression of organic field-effect transistors (OFETs) in flexible portable applications. Here, we have demonstrated RF sputtering deposited Ba0.5Sr0.5TiO3(BST) as high-k dielectric material for high performance operationally stable flexible low voltage operated OFETs. It was found that the BST deposition parameters can enormously affect the film properties like dielectric constant, surface morphology, and the crystallinity. The room-temperature-deposited BST films were found to be amorphous in nature with low leakage current, high dielectric constant, smoother surface morphology and high electromechanical stability. The fabricated flexible OFETs with optimized BST film have shown excellent electrical performance with max. field-effect mobility (μmax) of 1.01 cm2 V-1s-1 with near zero threshold voltage (VTH) and Ion/Ioff of ?105 while operating at -5 V. The fabricated devices were found to be operationally and electromechanically stable when subjected to various electrical and mechanical stress. The investigation has demonstrated that the proposed room-temperature-deposited BST is a suitable candidate for gate dielectric in low voltage operated, long-term electromechanical stable flexible OFETs. Copyright © 2020 American Chemical Society.