The 23-year-old Northern Ireland and Brentford striker netted just four times in 36 appearances for the Bees last term, but had previously shown a much more clinical touch in front of goal for Walsall.
Grigg bagged 20 goals in 45 matches for the Saddlers the season before, including a brace in Walsall's 4-2 win at stadium:mk on Boxing Day 2012, to establish himself as one of the hottest prospects in the Football League and feels the Dons' style of play can help him get back on track.
"When I was away before pre-season, I heard there was a bit of interest and when it came about, it was something I was really keen to do," Grigg told MK Dons Player. "As soon as the ball got rolling, both parties were confident they could make it work and it's just nice to be here now.
"There we a few choices but the style of football here suits me, it's a similar formation to Brentford and Walsall so it's a good fit for me personally. I know the Gaffer's wanted me for quite a while so it was really a no brainer. There was other clubs but this is the perfect fit.
"They have a great stadium and as soon as you come out onto the pitch it takes you back a little bit. I've had some good memories here and probably scored two of my best goals here, so hopefully I can add to that and make it a more regular occurrence."
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