Capped 17 times for the Wallabies during the 1970s, Monaghan made his debut on the wing against England at Twickenham in 1973. He was later a member of the 1975–76 tour of Britain, Ireland, where he featured in all four Tests against the home nations.[2] On the 1978 Wales tour of Australia, he kicked a famous drop goal for Sydney, from 45-metres and near the sideline, which put them ahead with two minutes remaining.[1][3]