After a permanent move for Besic fell through on deadline day, the Everton player will complete a season long loan switch in the coming days.
The 25-year old Bosnian had looked to have completed a £6 million move to The Riverside Stadium, however the deal fell through moments before the transfer window closed at 5pm.
It now appears that the Bosnia & Herzegovina international will return on loan again to Boro, where he spent the second half of the last season.
Reports also suggest Boro are still keen on bringing in another Everton player on loan. Yannick Bolasie had been linked with a permanent move however Everton firmly rebuffed any approach for the winger.