Police said they responded at about 1:40 a.m. at Barraco's Ristorante in the 3000-block of West 111th Street.
According to 19th ward Alderman Matt O'Shea, the victim was beaten by several suspects after they were asked to leave.
The man was taken to a hospital in with serious injuries to his head, police said.
Four suspects were taken into custody and have been charged, police said.
Further details were not immediately available.
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