Police conducted a sweep Wednesday and arrested six people, including the four teens.
Also charged in the attack were Jose Quijano, 20, George Quintero, 20, Raul Munoz, 19, Adan Valdez, 19, and Mohammed Hammoodi, 19.
A 10th man, Erick Munoz-Juarez, 21, was arrested in relation to the attack but has not been charged. He was released from jail after posting bail, records show.
Minutes after midnight on Sept. 4, two men were walking home on Plumer Street, down the street from Lions Park, when two of the suspects approached them, asked for their money and mentioned being in a gang, police said.
Soon, more suspected gang members approached the victims from another house. The victims tried to run.
"This kind of group mentality is more consistent with gang activity," said Lt. Mark Manley. "Intimidation through numbers is consistent with what we've seen with gang violence."
One of the pedestrians got away; the other didn't.
The group is accused of jumping the man, kicking and punching him on the ground, fracturing and cutting his face.
One of the men allegedly stole his wallet before they all ran away.
A witness called 9-1-1 and reported seeing some flee to a nearby house, which is where police went.
Officers found 20 to 25 local gang members or associates partying there. One man tried to run and was arrested.
Police found the victim's wallet on another person at the party and arrested them.
In all, three people were arrested at the party, another six on Wednesday. Hammoodi is considered a fugitive.
Munoz and Valdez are also fugitives, according to court records.
Manley credited gang detectives with linking all the suspects to the crime.
"Costa Mesa P.D., and especially the gang enforcement unit, has worked diligently to keep gang violence at a minimum these last few years," he said. "This is just another example of efficient and effective law enforcement to keep the community safe."
Quijano is charged with robbery and assault with a deadly weapon with gang enhancements. Quintero is charged with possession of stolen property and assault with a deadly weapon with gang enhancements.
Both have pleaded not guilty and are due back in court later this month.