Rathbone, who won 26 caps for Australia before retiring because of injury in 2009, benefited from another burst up the middle from Mogg to touch down in the corner four minutes before the break.
The South African-born winger showed he had lost none of his hard edge when he clattered into O’Connor eight minutes after halftime and forced the Wallabies back off the pitch for the remainder of the match.
With flyhalf Kurtley Beale also struggling with an injured arm, the Rebels were blunted as an attacking force and two Christian Lealiifano penalties and a rampaging run for a try from No. 8 Mowen took the Brumbies out to a healthy lead.
When replacement back row forward Jarrod Saffy was sin-binned with 11 minutes remaining, the fourth try for a bonus point looked inevitable and Coleman duly delivered by running straight through the hapless Beale.