In this paper we report an extension of our earlier results for Zn1-xMgxSe and low-Be Zn1-xBexSe to related ternary (high-Be Zn1-xBexSe and Zn1-xBexTe) and quaternary (Zn1-x-yMgxBeySe) alloys. ii dependence of defect structure on crystal composition, growth and thermal treatment is observed. X-ray diffraction was used for phase analysis and determination of lattice parameters. High-resolution transmission electron microscopy was used to compare kind and density of defect. Among the studied crystals, the lowest defect density was found for Zn1-x-yMgxBeySe.