The crystallization sequence and the structure of the crystalline phases which form during annealing of the Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass were investigated by X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy in combination with differential scanning calorimetric analysis. During isothermal annealing at temperatures below and above the calorimetric crystallization temperature nanosized quasicrystals form as a first step of the crystallization. In the course of further isothermal annealing by and by at least four intermetallic phases (Be2Zr, Zr2Cu, and two not yet fully identified ones) crystallize. Simultaneously the quasicrystals vanish. The complicated crystallization sequence is linked to a strong diffusion controlled decomposition of the alloy. The small mobility of the alloy components may be one reason for the good stability of the glass.