Combined effects of the quasi-biennial oscillation (QBO) and the 11-year solar cycle (SC) on the winter hemisphere are investigated with an idealized mechanistic circulation model of a stratosphere-troposphere coupled system. A zonal momentum forcing is imposed to mimic a westerly or easterly phase of the QBO and a heating anomaly associated with the SC is introduced around the stratopause. A series of long time integrations of 39,600 days are performed to obtain statistically significant results for forty-six combinations of these experimental parameters. The obtained dependence of the temperature response in the polar stratosphere on the combination of QBO and SC are qualitatively consistent with the observed responses. The difference in the winter polar stratosphere between the solar maximum and minimum phase is highly significant at above the 95% confidence level in many cases of the QBO westerly runs. The SC effect is, however, relatively small compared to the QBO effect.