Sunderland's table-topping Under-21 side showed the first team how to hold onto a 1-0 lead as they extended their advantage over rivals Manchester United to four points.
Victory at the Riverside Stadium against a youthful Middlesbrough side came via the boot of Carl Lawson, his fine 62nd strike enough to seal all three points.
The Tees-Wear derby may have lacked the profile, passion and intensity of the Tyne-Wear derby but this was a crucial win against bottom of the table Middlesbrough.
With Manchester United not in action this was a goalden opportunity for Andy Welsh's side to extend their slight advantage at the top of the Barclays Under-21 Premier League table.
United have three games in hand and remain firm title favourites but victory means Sunderland should at least now push them all the way.
Welsh named £8million summer signing Jeremain Lens in a strong starting line-up, with Wes Brown and Billy Jones also getting game time.
The Dutch winger, out for a month with a hernia, got some more vital minutes after recently playing 45 minutes in a behind-closed doors friendly win over Livingston.
The only notable absentees were winger Rees Greenwood, away on England Under-20 duty, while midfielder Martin Smith has joined League Two Carlisle United on loan.
With assistant manager Paul Bracewell watching on, this was a good chance for Jones and Lens to impress ahead of the crucial first team clash with West Brom a week Saturday.
Sunderland started brightly and should have taken the lead just four minutes in, Mikael Mandron firing narrowly over the bar from close range after good work by Ethan Robson.
Brown then had to be alert up the other end as Boro broke at speed, the veteran centre-half getting across well to deflect Joao Morelli's effort wide for a corner.
Ethan Robson had started the evening well in central midfield but his night finished early, going off after 15 minutes with an injury to his right leg.
His replacement Denver Hume was pushed wide left, with Lens playing a more central role and seeing more of the ball as a result.
He failed to take advantage of a good opening 20 minutes in though, Lens shooting well wide under pressure from Nathan McGinley.
A youthful Boro side - who had named only one senior player Rhys Williams in their starting line-up - were pushing Sunderland hard, with Welsh's side struggling to break them down.
Lewis Maloney saw his rasping effort fizz wide of the left-hand post on the half-hour mark as Boro looked to press the Cats back towards their own goal.
Beadling found himself in unfamiliar territory 32 minutes in, the defender's close-range shot saved point-blank by Joseph Fryer in the Boro goal following a Sunderland corner.
Sunderland were dominating the possession but like their first team counterparts in the opening 45 minutes against Newcastle, failed to take advantage.
It was the hosts that finished the half strongly though, with Maloney seeing his superb effort dip inches over the crossbar with Maksymilian Stryjek back-peddling furiously.
Half-Time: Boro 0 Sunderland 0
Lens, who saw plenty of the ball in the first half, should have opened the scoring after 53 minutes but he blasted the impressive Hume's cut-back high over the bar.
And they were almost immediately made to pay when Stryjek made a stunning save with his left foot on the line to deny sub Thomas McAloon's header from handing Boro the lead.
Beadling then produced a superb sliding block to deny Callum Cooke's goal-bound effort moments later.
Welsh's side were struggling to find any rhythm after the break but they took the lead just past the hour mark through Carl Lawson's fine effort.
He connected well with Tommy Robson's left-wing cross to divert the ball into the top right-hand corner of the net, leaving Fryer with no chance.
Bottom-of-the-table Boro were in desperate need of a win and threw everything at Sunderland in the final stages of the game.
Mark Kitching almost snatched an equaliser but his shot flew inches wide of the left-hand post, as Boro flooded forward in numbers.
Sunderland held firm despite a nervy end to seal a potentially-crucial three points.
Brown eased through the game at centre-back, his experience and reading of the game proving too much for the youthful Boro frontline, while Jones was steady alongside him.
Lens' workrate impressed further forward.
Title-chasing Sunderland's final two games of the season see them play Southampton at home (April 3) and Tottenham Hotspur away (April 11).
Full-Time: Boro 0 Sunderland 1
Boro (4-2-3-1): Fryer, Johnson, Burn (C), Williams, McGinley, Tinkler, Jones, Maloney, Morelli, Pattison, Cooke.
Subs: Kitching (for Pattison, 26), McAloon (for Morelli, 42), Elsdon (for Williams, 80)
Subs Not Used: Coddington (gk), Wheatley.
Sunderland (4-2-3-1): Stryjek, Jones, Brown, Beadling, T. Robson, E. Robson, Lawson, Agnew, Honeyman, Lens, Mandron.
Subs: Hume (for Ethan Robson, 16), Nelson (for Lens, 81), McEvoy (for Lawson, 90)
Subs Not Used: Talbot, Brady, McEvoy.
Booked: Honeyman (52, foul)
Goals: Lawson (62)
Referee: Alf Greenwood