We derive a two-stage model in which health plans first compete to be selected by employers and subsequently compete to be chosen by employees. We identify the key determinants of competition and show that increasing competition at one stage often comes at the expense of competition at the other stage. Many economists and policymakers have argued that in order to increase competition among health plans, employers should offer multiple plans and structure premium contributions to make employees more price sensitive. While our theoretical model shows that following this policy prescription may not actually lead to lower premiums, our empirical analysis provides some support for this recommendation. We also find that if employers instead pay the full premium, premiums increase when they offer additional plans. These results have important implications for both employers and policymakers.