Police say the robbers entered the businesses armed with a handgun and demanded money from the registers. In two incidents, they also took property from customers.
The robbers are described as black men wearing black hooded jackets, 18-30 years old, 5'8"-6'0", with medium builds. They may be driving a black, four-door vehicle, possibly a Chrysler, police say.
The Subway robberies have occurred between 7 p.m. and 11 p.m. The 7-Eleven incidents have occurred between 11 p.m. and 7:30 a.m.
According to a Community Alert issued by Grand Central Area detectives, the incidents have occurred in the Shakespeare, Austin, Albany Park, and Grand Central police districts.
Anyone who may information about the robberies is asked to call detectives at (312) 746-8362.
The Sun-Times Media Wire contributed to this report.