Giroux, a native of Ontario, was bypassed in the OHL draft, and was thus a free agent, able to ply his wares in rival leaves. Gatineau offered Giroux a try-out at the start of the season, and he seized the opportunity, playing admirably during training camp, and winning on spot the Olympiques roster. Giroux seized a key offensive role on the team almost immediately, picking up two points in his first game, and a three-point effort in only his third game. Giroux’s offensive game continued to impress, as he climbed among scoring leaders, and shot up the Central Scouting rankings.
Over the course of the season, Giroux was named the QMJHL Rookie of the Month twice – in December and March – and by the end of the season, he had surpassed highly-touted 16-year-old Angelo Esposito in rookie scoring, finishing the season with 39 goals and 103 points in 69 games. Giroux was named to the QMJHL All-Rookie Team.
2006-07: Giroux finished the regular season ranked fourth in the Q with 112 points (48 goals, 64 assists) in only 63 games. These totals included an impressive 20 power-play goals and two shorthanded tallies. He also boasted a league-best shooting percentage of 26.1. He was one of Team Canada’s final cuts for the WJCs, due mainly to the volume of experienced players returning from the previous year’s gold medal-winning squad. Following Gatineau’s first-round elimination from the QMJHL playoffs, Giroux signed an ATO with the Phantoms. He appeared in five games, registering two points (one goal, one assist) and six penalty minutes.
2007-08: In his third season with the Gatineau Olympiques (QMJHL), Giroux racked up 106 points (38 goals, 68 assists) in 55 games. He was called up to the Flyers for two games before being sent back to the juniors. He was a QMJHL First All-Star Team pick as well as a Canadian Major Junior First All-Star Team selection. He represented Team Canada at the WJC, netting two goals and four assists in seven appearances.