The victim, who's between 45 and 55 years old, was found behind the restaurant chain located on 10th Street West and Lancaster Boulevard around 8:27 a.m.
Los Angeles Sheriff's Department deputies say the assault occurred near the trash cans. The victim sustained injuries to her head and face.
"She was severely injured in her face. She had stab wounds and she appeared to be very beaten. She was non-responsive to any questioning," said Los Angeles County Sheriff's Department Sgt. Kevin Pearcy.
She was transported to Antelope Valley Medical Center, where she's listed in critical but stable condition.
A description of the suspect was not immediately released.
Anyone with information on the case was urged to contact the Los Angeles County Sheriff's Lancaster Station at (661) 948-8466.