After representing Australia at U-17 and U-20 level, the former Motherwell forward had to wait until February 2006 to win a full cap.
By that time, he had established himself as one of the best finishers in Scottish football and had been approached about playing for Scotland at both U-21 and senior level.
McDonald, now 25, was eligible to switch allegiance because of his Scottish parents and he was first approached about playing for Scotland by then U-21 coach Maurice Malpas when Berti Vogts was still in charge of the national squad.
The overtures from Malpas were rebuffed but the offer of a place in the senior squad followed under Vogts' successor, Walter Smith.
"That was even more of a tough decision," McDonald recalled. "I was getting frustrated at not being involved with the Socceroos at that time and I felt maybe it was my time to get an opportunity.
"Looking back at it now and the players that we have had in the past, I was wrong to think that, because the amount I have learned in the last couple of years has shown me why these players were playing at that top level."
McDonald has since established himself as a key member of the Australia squad gunning for a place in next year's 2010 FIFA World Cup™ finals in South Africa and is priming himself for next week's key qualifier in Japan.
"To go to a World Cup now that I'm playing at the highest level is a big opportunity," he said. "Now I see myself in a great position where I am part of the Socceroos and involved in every game so far and it would be nice to go and get a win in Japan."
McDonald's goalscoring form at Motherwell earned him a switch to Celtic at the start of last season and memorable UEFA Champions League goals against the likes of AC Milan and Manchester United have demonstrated his ability to mix with the very best.
"It's been great from day one for me (at Celtic)," he said. "I have made the impression but you've got to keep at it. My form dipped at the start of the season. I probably wasn't at my best, but I stuck at it and the gaffer has been keeping faith in me.
"I think I've improved as a player all round. I'm only 25 still and I'm learning a lot about the game."