Ontario won a bronze medal, defeating team Quebec 5–2 in the medal round. During 2002 he also made his first appearance for Team Canada playing in the non-IIHF sanctioned Eight Nations Cup, helping the team win a gold medal. Stewart made his IIHF international debut playing for Canada in the 2003 IIHF World U18 Championships in Yaroslavl, Russia. During the tournament he scored six goals, tying for fourth place in tournament scoring. His scoring success ranked him as the top goal-scoring Canadian; however, he contributed no assists, and finished third on the team in points. The Canadian team finished the preliminary round with a 2–2–1 record. In the elimination round they defeated the Slovakian team 3–0 to win the gold medal. At the end of the tournament Stewart was named to the All-Star team. Later that year Stewart represented the OHL in the 2003 ADT Canada-Russia Challenge. He scored one goal, helping the OHL win both their games, which contributed to a 5–1 series win for the Canadian Hockey League (CHL). The following year Stewart was selected to play for Canada in the 2004 World Junior Ice Hockey Championships in Helsinki and Hämeenlinna, Finland. Canada went unbeaten in the preliminary round and advanced to the final of the elimination round, where they faced the United States team. During the second period of the final, Stewart scored a goal to put Canada ahead 3–1. It was his third point of the game, as he had made assists in the two previous goals. However, Canada conceded three goals in the third period, losing 4–3 and receiving the silver medal. Stewart finished the tournament with 11 points, tying teammate Nigel Dawes and US player Zach Parise for the tournament lead in points scored. Having scored one more goal than Stewart and Parise, Dawes was officially named the tournament's leading scorer. Later in the year Stewart was selected to play in the 2004 ADT Canada-Russia Challenge as part of the OHL All-Stars team, and later he was named an alternate captain. He scored a short handed goal in the OHL's second game of the series, a 5–2 win. The OHL won both of its games in the series, helping the CHL to a 4–2 win in the series. In 2005 Stewart was again selected to play for Canada in the World Junior Championships in Grand Forks, North Dakota. Unlike in previous years, Stewart struggled