Barrios de Pennsylvania O
- Oak Lane-East Oak Lane (10)
- Oak Tree Hollow (1)
- Oakmont (5)
- Old City (90)
- Old Uptown Harrisburg (7)
- Olde Kensington (33)
- Olney (14)
- Orchard Park (4)
- Outer Kenhorst/Shillington (3)
- Outer Lancaster (40)
- Outer Muhlenberg Township (1)
- Outer Wilkes-Barre (4)
- Outer York/Valley View/Grantley (8)
- Outlying South Allegheny (17)
- Overbrook (2)
- Overbrook (45)
- Oxford Circle-Castor (16)