List of former members of the United States House of Representatives (O) Number of years/terms representative/delegate has served Number of years/terms representative/delegate has served

| Representative | Years | State_ | Party | Lifespan |
|---|---|---|---|---|
| Robert Orr, Jr. | 1825–1829 | Pennsylvania | Democratic | 1786–1876 |
| Godlove Stein Orth | 1863–1871 1873–1875 1879–1882 | Indiana | Republican | 1817–1882 |
| Solomon Ortiz | 1983–2011 | Texas | Democratic | 1937– |
| Bill Orton | 1991–1997 | Utah | Democratic | 1948–2009 |
| Edwin Sylvanus Osborne | 1885–1891 | Pennsylvania | Republican | 1839–1900 |
| Henry Z. Osborne | 1917–1923 | California | Republican | 1848–1923 |
| John Eugene Osborne | 1897–1899 | Wyoming | Democratic | 1858–1943 |
| Thomas B. Osborne | 1839–1843 | Connecticut | Whig | 1798–1869 |
| Tom Osborne | 2001–2007 | Nebraska | Republican | 1937– |
| Doug Ose | 1999–2005 | California | Republican | 1955– |
| Gayton P. Osgood | 1833–1835 | Massachusetts | Democratic | 1797–1861 |
| James H. Osmer | 1879–1881 | Pennsylvania | Republican | 1832–1912 |
| Frank C. Osmers, Jr. | 1939–1943 1951–1965 | New Jersey | Republican | 1907–1977 |
| Harold C. Ostertag | 1951–1965 | New York | Republican | 1896–1985 |
| Peter J. Otey | 1895–1902 | Virginia | Democratic | 1840–1902 |