We study the impact of permanent open market operations (POMOs) by the Federal Reserve on U.S. Treasury market liquidity. Using a parsimonious model of speculative trading, we conjecture that i) this form of government intervention improves market liquidity, contrary to conclusions drawn by existing literature; and ii) the extent of this improvement depends on the market’s information environment. Evidence from a novel sample of Federal Reserve POMOs during the 2000s indicates that bid–ask spreads of on-the-run Treasury securities decline when POMOs are executed, by an amount increasing in proxies for information heterogeneity among speculators, fundamental volatility, and POMO policy uncertainty, consistent with our model.