We investigate if Big 4 firms are asymmetrically more effective than non-Big 4 firms in monitoring income-increasing versus income-decreasing quarterly earnings management. We also study the Securities and Exchange Commission's (SEC) 2000 requirement that audit firm reviews of quarterly financial statements be completed prior to their filing with the SEC (“timely reviews”). We find Big 4 firms are more effective than non-Big 4 firms in curbing income-increasing earnings management around seasoned equity offerings (SEOs), but not income-decreasing earnings management around open market repurchases (OMRs). In the post-2000 period, after the SEC's mandate for timely reviews began, we find income-increasing earnings management around SEOs declined significantly, and this decline is primarily driven by the clients of Big 4 firms. We provide evidence that timely quarterly reviews improve earnings quality, especially when companies have incentives to engage in income-increasing accruals and are reviewed by Big 4 firms.