Oakley is a city in Contra Costa County, California, United States. The population was 25,619 at the 2000 census. However, there have been significant population increases since the census was taken. Oakley is part of the East Contra Costa Bicycle Plan, which has existing facilities in Oakley as well as plans for further expansion. Oakley apartments for rent comparison page shows most up to date rent information on Oakley apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.