| Middlesex to Oakley (California) | 2,499.95 mi (4,023.28 km) |
| Middlesex to Oakton (Virginia) | 188.95 mi (304.09 km) |
| Middlesex to Oakville (Missouri) | 854.72 mi (1,375.53 km) |
| Middlesex to Oatfield (Oregon) | 2,416.75 mi (3,889.39 km) |
| Middlesex to Ocala (Florida) | 898.02 mi (1,445.22 km) |
| Middlesex to Ocean Acres (New Jersey) | 58.61 mi (94.33 km) |
| Middlesex to Ocean City (New Jersey) | 90.41 mi (145.51 km) |
| Middlesex to Ocean Pines (Maryland) | 155.16 mi (249.70 km) |
| Middlesex to Ocean Pointe (Hawaii) | 4,944.84 mi (7,957.94 km) |
| Middlesex to Ocean Springs (Mississippi) | 1,064.79 mi (1,713.61 km) |
| Middlesex to Oceanside (California) | 2,394.76 mi (3,854.00 km) |
| Middlesex to Oceanside (New York) | 45.54 mi (73.29 km) |
| Middlesex to Ocoee (Florida) | 919.45 mi (1,479.72 km) |
| Middlesex to Oconomowoc (Wisconsin) | 740.22 mi (1,191.27 km) |
| Middlesex to Odenton (Maryland) | 156.20 mi (251.37 km) |
