A total of 180 officers raided 24 addresses in London, Oxford and Abingdon at 07:00 GMT on Tuesday.
Thames Valley Police has charged 14 men and five women for drug-related offences, including conspiracy to supply heroin and cocaine.
The raids were part of a new operation launched to fight "serious and organised crime".
Nineteen people have been charged following a series of drugs raids across London and Oxfordshire.