The Australian Under-23 international started just four league matches for the Hammers during his six years at Upton Park, while a serious knee injury affected his progress last season.
Garcia is now fully recovered from the problem, but has been allowed to join the U's on a free transfer.
He made his debut for
The 23-year-old spent part of the 2000-01 campaign on loan at Leyton Orient, and scored four goals in 18 appearances for the O’s.