The UK's Daily Mail newspaper published the photo of the two players posing with fans at around 03:50. local time on its website on Wednesday.
Beale and O'Connor, who play for Super Rugby side the Melbourne Rebels, watched from the sidelines as the Lions beat their team 35-0 on Tuesday in the final midweek match of their tour.
Beale has only just returned to rugby after taking four months off following a string of alcohol-related incidents, including punching team mates on a bus in South Africa.
"There has been a full and thorough investigation of the information," the Australian Rugby Union said in a statement.
"The two players were out last night, but they were not drinking - 10 witnesses we have spoken to corroborated that."
The statement added that after the match Beale and O'Connor went to a function at a club with Rebels team-mates and some Lions players before stopping to pick up food on the way home.
"Both players are adamant that they didn't drink and we have checked that out thoroughly. James O'Connor was driving. They have not broken any team protocols," the ARU said.
"These players have done nothing wrong. Within the team protocols, they are expected to behave responsibly and show common sense but there are no curfews in place."
The Wallabies lost the first Test 23-21 and Beale missed a last-minute penalty that would have sealed victory for the hosts after slipping on contact.
The second Test of the three-match series is in Melbourne on Saturday.