In 1986, O'Neal joined Merrill Lynch and, by the early 1990s, he was running Merrill's leveraged finance division. After spells as global head of capital markets and co-head of the corporate and institutional client group, he spent two years as CFO from 1998 to 2000. In 2000, he was appointed president of the U.S. Private Client Group, the first executive of the division that oversees Merrill's brokerage who had not himself been a broker. O'Neal led massive layoffs within the division.