This paper uses confidential portfolio holdings data to show that corporate quantitative easing (QE) operates primarily through a liquidity demand channel. By acting as a standing buyer, the central bank enhances bond liquidity, raising demand from liquidity-sensitive investors. The impact on prices crucially depends on investor heterogeneity. Mutual funds rebalance toward eligible bonds, while banks and foreign investors are net sellers. As a result, mutual funds amplify the transmission of QE to bond prices. QE mainly compresses the CDS-bond basis with limited effect on default premia. Even during balance sheet unwinding, the implicit liquidity backstop persists, muting quantitative tightening effects.