American soccer writing, history & data.
| Team | Location | Years |
|---|---|---|
| Oakland Clippers | Oakland, CA | 1967–1968 |
| Oakland F.C. | Oakland, CA | 1910–1910 |
| Oakland F.C. | Oakland, CA | 1910–1911 |
| Oakland/Golden Bay Buccaneers | Berkeley, CA | 1976–1976 |
| Oakland Hornets A.F.C. | Oakland, CA | 1903–1909 |
| Oakland Rangers F.C. | Oakland, CA | 1913–1914 |
| Oakland Roots S.C. | Oakland, CA | 2019 |
| Oakland Stompers | Oakland, CA | 1978–1978 |
| O'Brien Live Wires | St. Louis, MO | 1912–1913 |
| Occidental A.C. | San Francisco, CA | 1903–1905 |
| Oertli Markets | Milwaukee, WI | 1935–1936 |
| Ohio XOGGZ | Dublin, OH | 1996–1996 |
| Okanagan Challenge S.C. | Kelowna, BC | 1990–2012 |
| Oklahoma City Alliance | Oklahoma City, OK | 1996–1998 |
| Oklahoma City Heat | Oklahoma City, OK | 1996–1996 |
| Oklahoma City Slickers | Oklahoma City, OK | 1982–1983 |
| Oklahoma City Slickers | Oklahoma City, OK | 1993–1993 |
| Oklahoma City Slickers | Oklahoma City, OK | 1994–1996 |
| Oklahoma City Spirit S.C. | Oklahoma City, OK | 1990–1992 |
| Oklahoma City Stampede | Oklahoma City, OK | 1984–1984 |
| Oklahoma City Warriors | Oklahoma City, OK | 1986–1993 |
| Oklahoma City Warriors | Oklahoma City, OK | 1993–1994 |
| Oklahoma City Warriors | Oklahoma City, OK | 1998–1998 |
| Oklahoma City Warriors/Hatters | Oklahoma City, OK | 1998–1998 |
| Oklahoma City Wind | Oklahoma City, OK | 1999–1999 |
| O'Learys | St. Louis, MO | 1910–1912 |
| Olympia S.C. | New Britain, CT | 1965–1967 |
| Olympic Club | San Francisco, CA | 1914–1921 |
| Omaha Flames | Omaha, NE | 1996–1998 |
| Orange County Zodiac | Irvine, CA | 1997–1999 |
| Orlando Ladyhawks | Orlando, FL | 1998–1998 |
| Orlando Lions | Orlando, FL | 1986–1990 |
| Orlando Lions | Orlando, FL | 1992–1996 |
| Orlando Lions | Orlando, FL | 1994–1994 |
| Orlando Nighthawks | Orlando, FL | 1998–1999 |
| Orlando Sundogs | Orlando, FL | 1997–1997 |
| Oscar Mayer Co. | Madison, WI | 1934–1936 |
| Oshkosh Aurochs | Oshkosh, WI | 1954–1964 |
| Oshkosh Sport Club | Oshkosh, WI | 1927–1938 |
| Oshkosh Sport Club 2nd | Oshkosh, WI | 1932–1934 |
| Oster S.C. | Racine, WI | 1952–1996 |
| Oster S.C. Reserves | Racine, WI | 1957–1969 |