New glasses have been synthesized in the quaternary system based on complex molybdenum oxyfluorides. Systematic investigations were implemented in the MoO3-BaF2-NaF-ZnF2 quaternary system with a constant amount (30 mol%) of MoO3. Samples of a few mm in thickness were obtained. The physical properties such as density, molar volume, glass transition temperature, activation energy of crystallization, stability criterion, thermal expansion coefficient, refractive index, molar refractivity and infrared measurements were performed and correlated with composition, especially with alkali fluoride content. By comparison with standard fluoride glasses, these glasses exhibit similar characteristic temperatures but higher refractive index and high ultraviolet absorption.