Birchall had an exceptional first season in 2006 with the Hawthorn, playing 16 games out of a possible 22. The Tasmanian was chosen at pick 14 in the 2005 AFL Draft and made his debut in the number 35 guernsey in Hawthorn's opening match of the season against Fremantle at Aurora Stadium in his home state, Tasmania.
All year, Birchall excelled across half-back for the Hawks, mainly highlighted by an impressive 23 touches in the big loss to St Kilda in round 13 and 27 touches and 10 marks in a sloggish win against the Kangaroos in round 21. To finish off the season, Birchall finished off with his best game yet- a massive 36 touches and 11 marks in the 10-goal win against Geelong.
At season's end, Birchall came sixth in the NAB AFL Rising Star, won Hawthorn's Best First Year Award and was given the number 14 jumper for the 2007 season, left vacant by Harry Miller, who was delisted by Hawthorn at the end of 2006. Grant Birchall attended St Brendan Shaw College in Devonport, Tasmania.
2007 saw Birchall play every game for Hawthorn, and consolidate his role as a running half-back with poise and neat disposal. Many pundits are expecting the low-key young Hawk to make further progress in 2008, possibly including stints further up the ground.
Birchall played in his first AFL Premiership in 2008, when the Hawks defeated reigning premiers Geelong. Birchall lost half of his two front teeth in a collision during the match.
In 2012, Birchall had his best season to date. Birchall averaged 23.1 disposals in his 21 games in the Home and Away season with an incredible disposal efficiency of 85%. Birchall was rewarded with his first All-Australian Guernsey.