The men left after unleashing their barrage, but not before one of them was tackled on Logan Park by university deputy proctor Andrew Ferguson.
The incident occurred early in what was a mostly incident-free start to the event, held at at Forsyth Barr Stadium. Police attended and removed the man.
OUSA president Laura Harris said there was ‘‘a lot of energy, a lot of enthusiasm, and it was great to see all the freshers really engaging with this event''.
Of the egg-throwing, she said: ‘‘A couple of people are always going to play up, and it's a really unfortunate incident. The rest of them seem to be completely behaving.''
OUSA communications manager Tess Trotter said a range of safety services were in place last night.
The OUSA's Are You OK? team - a group of student volunteers who look after people who were too intoxicated, or needed help - was on the job.
They also offered rides to people who needed to go home.
The Red Frogs support network, a charity organisation, also provided food and rides, and St John was on site.
Ms Trotter said there was a strong security presence, and students over the age 18, who could buy beer, wine and RTDs at the event, were in a separate area to the 17-year-olds.
Few students appeared intoxicated when they arrived at the stadium by bus, although one woman was seen staggering and vomiting, and some men were urinating on trees.
Mr Ferguson referred questions to the university communications team, which did not respond to calls last night.
