Eighteen-year-old Makenzie Anthony Corkill punched the victim multiple times after throwing him on the ground.
He admitted common assault and was also ordered to pay £50 prosecution costs.
A second charge, of being drunk and disorderly, was withdrawn by the prosecution in light of the guilty plea.
Prosecuting advocate Hazel Carroon told the court that Corkill had been removed from the Outback by security staff on March 16, at 2.30am, after an incident with the complainant inside the pub.
The complainant then left the bar and Corkill, who was still outside, grabbed him and threw him to the ground.
The teenager then punched him multiple times in the head, before the bouncers separated them.
Corkill, who lives at Springfield Avenue, was interviewed and told police that he had a historical issue with the male.
The court heard that he has no previous convictions.
Defence advocate Emily Brennan asked for credit to be given for her client’s guilty plea and his lack of previous convictions.
She added that he had made admissions to the police and had co-operated fully.
Ms Brennan said that there had been underlying issues between the two parties and seeing the complainant had antagonised Corkill.
The advocate said that the injuries as a result of the assault had been low level and that it had not been a sustained attack.
Deputy High Bailiff Rachael Braidwood ordered the defendant to pay the fine and costs at a rate of £100 per month.