Barrier materials are desirable for efficient ZnO-based optoelectronic devices. However, the BeZnO ternary alloy suffers from severe phase segregation due to considerable deformation in the local structure caused by the large lattice misfit between ZnO and BeO. In this work, we proposed an effective method, called complementary in bond lengths, through which the local bond length deviation in BeZnO alloy system could be greatly reduced by introducing chemical bonds with opposite misfits. Our density functional theory calculations showed an improved thermal stability of BeZnOS quaternary alloy. The formation energy of BeZnOS quaternary alloy decreased when S atom appropriately occupied O lattice site. The stabilizing mechanism for S incorporating BeZnO was discussed by analyzing the relaxed atomic configurations and local bonds in BeZnOS quaternary alloy. It was suggested that the BeZnOS quaternary alloy system with an improved stability are suitable for engineering the energy band-gap of ZnO materials in ultraviolet region.