This work shows that the crystallization process of Zr–Ni–Cu–Al metallic glass is greatly influenced by adding Nb as an alloying element. Based on the results of the differential scanning calorimetry experiments for metallic glasses Zr69−xNbxNi10Cu12Al9 (x = 0–15 at. %), the crystallization process takes place through two individual stages. For Zr69Ni10Cu12Al9 (x = 0), metastable hexagonal ω-Zr and a small fraction of tetragonal Zr2Cu are precipitated upon completion of the first exothermic reaction. Contrary to this alloy, the precipitation of a nanoquasicrystalline phase is detected when 5–10 at. % Nb is added. Furthermore, the crystallization temperature Tx, supercooled liquid region ΔTx and reduced temperature Tg/TL (Tg is the glass transition temperature, TL the liquidus temperature) increase with increasing Nb content. These results indicate that adding Nb content to Zr–Ni–Cu–Al metallic glasses not only induces quasicrystalline phase formation, but also enhances glass-forming ability. © 2001 American Institute of Physics.