High-temperature plastic flow and tensile ductility in pre-annealed Zr65Al10Ni10Cu15 bulk metallic glass are examined in a supercooled liquid region. The specimen annealed at 673K for 1.8ks before the tensile test exhibits uniform deformation, and large elongation of 1100% is obtained in the tensile test at 673K and in a constant true strain rate of 1×10-2s-1. In the specimen, initial stress decreases in comparison with that of the specimen without annealing, but apparent strain hardening arise during deformation. SEM analysis after the deformation reveals that the cavitation is very limited even at the fracture tip. XRD and TEM analyses reveal that icosahedral phase is observed only in gage section but not in grip section after the deformation. The limited cavitation due to the accommodation of stress concentration through the grain boundary amorphous phase possibly makes a positive contribution to the large elongation in the annealed specimen, as well as the neck stability due to the strain hardening by the interaction between the icosahedral phase particles increasingly crystallized by the local strain.