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In this work, c -axis preferentially oriented Be x Zn 1- x O 1- y S y (BeZnOS) quaternary alloy films were prepared successfully on c -plane sapphire by pulsed laser deposition for the first time. By appropriate adjustment of O 2 pressure during the deposition, the grown films exhibited a single-phase hexagonal structure and good crystalline quality. The solid solubility of S in Be x Zn 1- x O 1- y S y quaternary alloy was significantly expanded ( y ≤ 0.17 or y ≥ 0.35) as a result of simultaneous substitution of cation Zn 2+ by smaller Be 2+ and anion O 2− by bigger S 2− . Besides, due to the introduction of BeO with a wide band gap, BeZnOS quaternary films exhibited wider band gaps than the ternary ZnOS films with similar S contents. As the O 2 pressure increased from 0.05 Pa to 6 Pa, the band gap of BeZnOS displayed an interesting bowing behavior. The variation range of the band gap was between 3.55 eV and 3.10 eV. The BeZnOS films with a wide band gap show potential applications in fabricating optoelectronic devices such as UV-detectors. [ABSTRACT FROM AUTHOR]