Investigators say two of the men enter the banks yelling and cussing and demanding that everyone inside drops down on the floor. One of the robbers then jumps over the teller counter and opens the gate to the teller area to let the second robber in.
The robbers are known as the "Pop the Lock Crew" because the FBI says they use a pry tool to open locked teller drawers and remove cash.
In each of the robberies, the men jumped into another vehicle driven by a getaway driver. Those vehicles have all been reported stolen in Los Angeles County.
The robbers have worn athletic clothing and masks. During one of the robberies, a suspect removed his mask as he was leaving, and a security camera captured his image.
Anyone with information on the robbers is asked to call the Orange County Sheriff's Department at (866) TIP-OCSD or (866) 847-6273.
City News Service contributed to this story.