Barnard, who plied his trade for Leyton Orient last season, has penned a deal with the Gravelmen until January with an option to extend his contract in the new year.
The 23-year-old was released by the O's and made his Grays debut in the 1-0 win over Altrincham on the weekend.
Grant, who is also 23, joins the Blue Square Premier club on a year-long loan and is no stranger to the Recreation Ground after a spell with the club last season.
However, he was forced to leave the club last year due to legal complications which saw him end up in court.
He rejoins Grays after being acquitted of all charges.
Source: http://www.confguide.com/newsArticle.do?id=6965