The 31-year-old was released by Second Division outfit Bristol City at last season's end before joining the Whaddon Road outfit for a trial last month.
Robins boss Bobby Gould decided against offering the former Bristol Rovers and Notts County hit-man a contract with the Gloucestershire-based club last week.
Beadle has decided to take a trial with The Bees and played with the South West London club in a pre-season friendly against Conference club Farnborough on Saturday.
Beadle was pleased with his performance for manager Wally Downes' side and hopes it will lead to him landing a deal at Griffin Park.
"Personally it couldn't have gone any better," Beadle told the club's official website.
"I've scored a goal, got a penalty, laid on a couple of chances for the lads, and generally thought my all-round game was not too bad.
"I'm just pleased I'm able to play. It's a good bunch of lads, a young squad.
"They are all prepared to dig-in, which is always a benefit."
