His next task is to take things to the finish line.
Peterson, who served as premier between 1985 and 1990, was named chair of the TO2015 organizing committee Monday afternoon. He replaces Roger Garland, who has held the job since 2009.
Peterson was the chair of Ontario's bid to get the Games. He was joined by Garland, chief executive officer Ian Troop and dozens of TO2015 staffers for the announcement at the organization's downtown office.
Peterson, who was nominated to the position by Premier Kathleen Wynne, thanked Garland for his efforts in creating a strong foundation over the last few years.
"Think of it this way — Roger was the cake and I'm the icing," Peterson said with a smile. "And I get to do all the good stuff. Roger has done all the donkey work. He has put this organization together on a sound financial basis, great people have been hired across the board, all the wheels are moving together and in a very thoughtful way."
The Pan Am Games will be held from July 10-26, 2015 in several communities across the province. The Parapan Games are slated for Aug. 7-14.
Garland didn't offer specifics on reasons for his departure and did not take questions from reporters. A news release said he would be moving on to new opportunities.
"In short, now is the perfect time for transition," he said in a statement. "I've accomplished what I set out to do. To use an appropriate sports analogy, I'm passing the baton for the next racer to carry for the final 100 metres of the relay race, confident that I've done my part to ensure the team's success."
Garland told staffers in attendance there was a "lot of disappointment" but that there were many good things about the transition.
"I think there are those phases of grief you go through when you've lost something and yet there is a positive side to it," he said, adding he's looking forward to spending more time with his wife, who will retire at year's end.
Garland, who plans to formally step down at a board meeting on Thursday, also said that he's very proud of the organizing team's effort.
"We've built an organization and a structure and a plan to put on the biggest Games in this country's history and we've done it with a lot of constraints and a lot of discipline," he said.
"So all I can say is I am just in awe of what you folks have done and I've got enormous confidence going forward that you're going to continue to do what you've done up until now."
Peterson is a senior partner and chairman of Cassels Brock LLP, where he practises corporate and commercial law. He was the founding chairman of the Toronto Raptors and also served as chancellor of the University of Toronto until June 2012.