| Senate Name | County | Dist. # | Party | Session # | Dates | Notes |
|---|
|
|
| O'Connell, Frank J. | 20 | Pike, Wayne, Wyoming, Monroe (Part), Luzerne (Part), Bradford (Part) | Rep | 163-4 | 1979-80 |
| O'Connell, Frank J. | 20 | Pike, Wayne, Wyoming, Monroe (Part), Luzerne (Part), Bradford (Part) | Rep | 165-6 | 1981-82 |
| O'Connell, Frank J. | 20 | Pike, Susquehanna, Wayne, Wyoming, Monroe (Part), Luzerne (Part) | Rep | 167-8 | 1983-84 |
| O'Connell, Frank J. | 20 | Pike, Susquehanna, Wayne, Wyoming, Monroe (Part), Luzerne (Part) | Rep | 169-70 | 1985-86 |
| O'Neill, Charles | 1 | Philadelphia City | Whig | 77 | 1853 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 157-8 | 1973-74 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 159-60 | 1975-76 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 161-2 | 1977-78 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 163-4 | 1979-80 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 165-6 | 1981-82 |
| O'Pake, Michael A. | 11 | Berks (Part), Montgomery (Part) | Dem | 167-8 | 1983-84 |
| O'Pake, Michael A. | 11 | Berks (Part), Montgomery (Part) | Dem | 169-70 | 1985-86 |
| O'Pake, Michael A. | 11 | Berks (Part), Montgomery (Part) | Dem | 171-2 | 1987-88 |
| O'Pake, Michael A. | 11 | Berks (Part), Montgomery (Part) | Dem | 173-4 | 1989-90 |
| O'Pake, Michael A. | 11 | Berks (Part), Montgomery (Part) | Dem | 175-6 | 1991-92 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 177-8 | 1993-94 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 179-80 | 1995-96 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 181-2 | 1997-98 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 183-4 | 1999-00 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 185-6 | 2001-02 |
| O'Pake, Michael A. | 11 | Berks (Part) | Dem | 187-8 | 2003-04 |
| Oesterling, Donald O. | 21 | Butler, Lawrence | Dem | 149-50 | 1965-66 |
| Oesterling, Donald O. | 21 | Butler, Lawrence | Dem | 151-2 | 1967-68 |
| Oesterling, Donald O. | 21 | Butler, Lawrence | Dem | 153-4 | 1969-70 |
| Oesterling, Donald O. | 21 | Butler, Lawrence | Dem | 155-6 | 1971-72 |
| Ogle, Alexander | 22 | Bedford, Somerset | Dem | 50 | 1825-26 |
| Ogle, Alexander | 22 | Bedford, Somerset | Dem | 51 | 1826-27 |
| Ogle, Alexander | 22 | Bedford, Somerset | Dem | 52 | 1827-28 |
| Ogle, Alexander | 22 | Bedford, Somerset | Dem | 53 | 1828-29 |
| Olmstead, Arthur G. | 13 | Clinton, McKean, Potter, Tioga | Rep | 93 | 1869 |
| Olmstead, Arthur G. | 13 | Clinton, McKean, Potter, Tioga | Rep | 94 | 1870 |
| Olmstead, Arthur G. | 13 | Clinton, McKean, Potter, Tioga | Rep | 95 | 1871 |
| Orie, Jane Clare | 40 | Allegheny (Part), Butler (Part), Westmoreland (Part) | Rep | 185-6 | 2001-02 |
| Orie, Jane Clare | 40 | Allegheny (Part), Butler (Part), Westmoreland (Part) | Rep | 187-8 | 2003-04 |
| Orlando, Quentin R. | 49 | Erie (Part) | Dem | 157-8 | 1973-74 |
| Orlando, Quentin R. | 49 | Erie (Part) | Dem | 159-60 | 1975-76 |
| Orlando, Quentin R. | 49 | Erie (Part) | Dem | 161-2 | 1977-78 |
| Orlando, Quentin R. | 49 | Erie (Part) | Dem | 163-4 | 1979-80 |
| Orr, Robert, Jr. | 24 | Venango, Warren, Armstrong, Indiana, Jefferson, Cambria | Dem | 47 | 1822-23 |
| Orr, Robert, Jr. | 24 | Venango, Warren, Armstrong, Indiana, Jefferson, Cambria | Dem | 48 | 1823-24 |
| Orr, Robert, Jr. | 24 | Venango, Warren, Armstrong, Indiana, Jefferson, Cambria | Dem | 49 | 1824-25 |
| Orth, Henry | | Berks, Dauphin | Rep | 26 | 1801-02 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 106 | 1885-86 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 107 | 1887-88 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 108 | 1889-90 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 109 | 1891-92 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 110 | 1893-94 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 111 | 1895-96 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 112 | 1897-98 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 113 | 1899-00 |
| Osbourn, Francis A. | 3 | Philadelphia (Part) | Rep | 114 | 1901-02 |
| Osterhout, Peter M. | 11 | Bradford, Susquehanna, Wyoming | Rep | 93 | 1869 |
| Osterhout, Peter M. | 11 | Bradford, Susquehanna, Wyoming | Rep | 94 | 1870 |
| Osterhout, Peter M. | 11 | Bradford, Susquehanna, Wyoming | Rep | 95 | 1871 |
| Overfield, William A. | 8 | Schuylkill, Carbon, Monroe, Pike | Dem | 71 | 1847 |
| Overfield, William A. | 8 | Schuylkill, Carbon, Monroe, Pike | Dem | 72 | 1848 |
| Overfield, William A. | 8 | Schuylkill, Carbon, Monroe, Pike | Dem | 73 | 1849 |
| Owlett, G. Mason | 25 | McKean, Potter, Tioga | Rep | 130 | 1933-34 |
| Owlett, G. Mason | 25 | McKean, Potter, Tioga | Rep | 131 | 1935-36 |
| Owlett, G. Mason | 25 | McKean, Potter, Tioga | Rep | 132 | 1937-38 |
| Owlett, G. Mason | 25 | McKean, Potter, Tioga | Rep | 133 | 1939-40 |