The pair, both 26, completed permanent moves to the Riverside Stadium although the fees have not been disclosed. It is understood the McDonald deal was delayed as the two side squabbled over a fee, believed to be around $6million.

Middlesbrough boss Gordon Strachan had already added to his squad in the transfer window with the signings of Barry Robson, Willo Flood and Chris Killen from Celtic, together with the loan additions of Stephen McManus and Kyle Naughton.

Australia international McDonald scored 50 goals in 88 league appearances for Celtic after joining the club in the summer of 2007.

Miller, meanwhile, has passed double figures for Aberdeen in the past two seasons and earned his second Scotland cap in November.

A busy deadline day at The Riverside saw highly-rated youngster Adam Johnson secure a move to Manchester City for an undisclosed fee.

Boro's Egypt international striker Mido was set to join West Ham for the remainder of the campaign after spending the first half of the season on loan at Zamalek back in his homeland.

And Boro also agreed to cancel the contract of young winger Nathan Porritt to allow him to leave the club with immediate effect.