Barnsley have reluctantly decided to sell the trio as part of their cost-cutting measures in the wake of their relegation to League One.
The Tykes are willing to listen to offers for the players, who are among their highest earners at Oakwell, so that they can fulfil the criteria of the Salary Cost Management Protocol.
The news has alerted a number of Championship sides to the availability of the trio with the three players sure to have no shortage of suitors after impressing at Oakwell.
O'Grady, who finished as top scorer at Barnsley last season, came close to a move to Charlton earlier this summer only for the move to fall through at the final minute and a host of sides are believed to keeping tabs on his situation.
Cranie joined Barnsley on a free transfer in 2012 and established himself as a key performer in the side going on to pick up the captain's armband.
Kennedy also moved to Barnsley on a free transfer in 2012 and has been first-choice left-back since his arrival.