The thefts have been reported in the 1700 block of Robin Ave., the 2900 block of Bowen St. and the 1100 block of High Ave.
Police say the thieves are then selling or trading what they steal in exchange for drugs including heroin, marijuana and prescription medications.
Oshkosh police are reminding drivers to leave nothing valuable in their vehicles, including loose change, power cords for electronics, purses and laptop computers. Drivers are also reminded to lock their car doors, as thieves will often hit the easiest target, pulling on door handles until they find one that is unlocked.
It is also being recommended to lock house doors, even when someone is home.