This paper analyzes the dynamics of rate of return for postgraduate education and the determinants of wage premiums for postgraduate labor, especially for the impact of higher education expansions, in terms of quantity and quality, since the late 1990s in Taiwan. Utilizing quasi-panel data over the 1990-2004 period and employing the double fixed effect model, the empirical results first confirm the existence of wage premiums for workers with postgraduate degrees. However, the analysis on the dynamics of wage premiums finds that it ranged from only 1.40% to 11.67% and decreased sharply in 2004, indicating that the pecuniary reward for postgraduate qualification seems to not be as high as expected. Along with the rapid expansion of higher education, the concerns about its negative impact on rate of returns to education is witnessed in this study. The sharp increase in the supply of postgraduate labors appears to have a negative impact on an individual’s wage premium. Similarly, a decline in the postgraduate labor quality along with higher education expansion has contributed to a negative wage effect.