The structure and the crystallization behavior of the bulk metallic glass Zr46.8Ti8.2Ni10Cu7.5Be27.5 and of its Be-free derivative Zr64.5Ti11.4Ni13.8Cu10.3 are analyzed by means of differential scanning calorimetry, transmission electron microscopy, and x-ray diffraction. These alloys reveal different glass forming abilities. Thermal stability and crystallization behavior of the glasses are also different. These differences are correlated with the different degrees of icosahedral short range order in the glasses. Results fit to the model of geometric frustration, which describes the structure of metallic glasses as “highly defective quasicrystals.” In the present case Be degrades the ideal quasicrystalline structure.