In this work, the time-dependent plastic deformation behavior of Ti40Zr25Ni3Cu12Be20 bulk and ribbon metallic glass alloys was investigated using a nanoindentation technique at room temperature with the applied load ranging from 5 to 100 mN. The stress exponent n, defined as, has been derived as a measure of the creep resistance. It was found that the measured stress exponent increases rapidly with increasing indentation size, exhibiting a positive size effect. The size effect on the stress exponent n obtained from the bulk sample is more pronounced than that obtained from the ribbon sample. The deformation mechanism involved will be discussed.