On leaving the department, Coleman returned to Philadelphia and subsequently became a partner in the Washington office of the Los Angeles-based law firm O'Melveny & Myers. Colman argued a total of 19 cases before the Supreme Court. He appeared for the respondent in the argument and reargument of "Garcia v. San Antonio Metropolitan Transit Authority" (1985). In 1983, with the election quickly approaching, the Reagan administration stopped supporting the IRS's position against Bob Jones University that overtly discriminatory groups were ineligible for certain tax exemptions. Coleman was appointed to argue the now unsupported lower court position before the Supreme Court, and won in "Bob Jones University v. United States".