The 23 year old joins the Roughyeds after leaving Championship side Dewsbury Rams.
Bentley made 12 appearances for Dewsbury during his first Championship campaign before leaving the club last week to complete the move to Oldham.
He is eligible to make his debut when the Roughyeds face Barrow Raiders at Boundary Park on Sunday.
The forward has strong family links with the club. His father, Valu Bentley, made 58 appearances for Oldham during a three season spell between 2010 and 2012.
French born Bentley began his career in the Wigan Warriors academy before moving into rugby union, where he was part of the Sale Sharks youth set up.
He later represented Fylde and Sedgley Tigers and played for Lancashire in 2023 before returning to rugby league. He also impressed with Leigh Leopards reserves before joining Dewsbury.
Oldham coach Alan Kilshaw welcomed the signing and believes Bentley will strengthen his squad.
He said, "We're really pleased to have brought Tane to the club.
"He is a great prospect, and we feel he will flourish in our environment obviously there is a family link, too, with his father playing for the club.
"This signing adds depth. He can play on an edge, and he can play in the middle he is very comfortable doing that.
"He has a rugby union background and has done really well in league over the last few years, notably while at Leigh reserves last year, where he was one of their standout performers."
Bentley will now compete for a place in the squad ahead of Sunday's Championship fixture against Barrow Raiders.
