The England striker joined the North London club from Manchester United on transfer deadline day, and after failing to get off the mark in his first two appearances, it was third time a charm for the 23-year-old at Villa Park.
He was the provider for the opening goal, playing through Mesut Ozil to score on 32 minutes, before the German World Cup winner returned the favour two minutes later as Welbeck finished from close-range. An own goal from Aly Cissokho ensured the visitors a three-goal victory.
England internationals Calum Chambers, Alex Oxlade-Chamberlain and Kieran Gibbs were also included in Arsene Wenger’s starting line-up and Fabian Delph was in Villa’s midfield.
Fabian Delph featured for Villa
Three Lions boss Roy Hodgson was in attendance at The Liberty Stadium as Swansea welcomed Southampton to Wales.
Fraser Forster and Ryan Bertrand, both senior internationals, and U21 midfielder James Ward-Prowse all featured for the Saints, who claimed a 1-0 win thanks to Victor Wanyama.
Jack Colback saw his side come from two behind to earn a share of the spoils. A late Pappis Cisse double rescued Newcastle United against Hull City in a match that finished two-apiece.
In Saturday’s earlier game, Steven Caulker scored as QPR drew 2-2 at home to Stoke City, with Peter Crouch, who won 42 caps for the Three Lions, getting himself on the scoresheet for the visitors.
Raheem Sterling was among the goals at Upton Park – but his effort was not enough to stop Liverpool slipping to defeat.
The 19-year-old took his tally to three goals this season on 27 minutes – pulling the score back to 2-1 after early strikes from Winston Reid and Diafra Sakho had given the Hammers the lead.
But that was the only bright spot for the England players on show at Upton Park as the home side recorded a 3-1 victory.
Jordan Henderson was at the heart of the Liverpool midfield while substitutes Adam Lallana and Rickie Lambert failed to make an impact after coming off the bench.
Patrick Roberts appeared as a sub for Fulham
Moving to the Championship, and U19 winger Patrick Roberts came close to snatching a point for ten-man Fulham at home to Blackburn Rovers.
Hugo Rodallega almost gave the Cottagers the lead with a rasping effort that whistled just wide of the post from 25 yards on 34 minutes, before Shaun Hutchinson saw red for the hosts moments before the break for a reckless tackle on Lee Williamson.
Things got worse for Fulham on 58 minutes as Jordan Rhodes cooly finished right-footed to give Rovers the lead.
The home side retaliated, and former England midfielder Scott Parker charged forward to start a counter that led to Ross McCormack finding himself free to shoot at goal, but he was denied by former U21 goalkeeper Jason Steele’s right foot.
McCormack then pulled another effort wide of the post before Roberts was introduced to the action with seven minutes remaining as caretaker manager Kit Symons urged his side forward.
With two minutes remaining, Roberts received a quick free-kick from McCormack, and he cut inside past a defender before letting rip with a left-footed strike, but Steele got down well to deny him and ensure his side picked up the points.
Demarai Gray scored for Birmingham City
Over in Norfolk, and it was the battle of the wingers at Carrow Road as Nathan Redmond’s Norwich City side came from two goals down to draw with Demarai Gray’s Birmingham City.
And it was U19 international Gray who took the early initiative – firing his side into a 2-0 lead shortly before the half-time break.
The Canaries hit back when Cameron Jerome halved the deficit seven minutes after the restart before Gray was withdrawn from the action for the visitors.
Norwich continued to press, and Redmond, an U21 regular, provided the cross that led to the equaliser - Jerome heading home to level.
Bamford celebrates his strike for 'Boro (MFC/Varley Picture Agency)
Patrick Bamford, another who has represented Gareth Southgate’s side, grabbed his first goal for Middlesbrough as they picked up three points against Brentford at The Riverside.
The on-loan Chelsea forward popped up with a header in a 4-0 win for the north east side – which also included fellow U21 international Ben Gibson in defence.
Jordon Ibe, a member of Aidy Bothroyd’s U20 squad, notched for Derby County as they battled back to earn a point against Cardiff City.
Aron Gunnarsson had put the Welsh side ahead after Matthew Connolly flicked on a corner, and Peter Whittingham doubled their lead with a left-foot strike.
Derby hit back when Cyrus Christie laid on a perfect ball for Ibe, on-loan from Liverpool, to convert and that was followed by Craig Bryson’s equaliser from long distance. Will Hughes, an U21 regular, played the full match for the Rams.
Dele Alli scored a hat-trick for MK Dons
Lewis Cook, who helped the U18s to two victories over Holland earlier this month, was part of the Leeds United side that defeated Huddersfield Town 3-0 at Elland Road.
Dele Alli celebrated his new contract with MK Dons by grabbing a hat-trick as Crewe Alexandra were hit for six at Stadium MK.
The U19 midfielder sealed his treble on 84 minutes as his side ran out 6-1 winners.
Dons manager Karl Robinson told the BBC afterwards: "The chairman said it's the best individual performance he's seen at the football club.
"He does all the talking with a football, I don't have to talk about him. The fans have got a local hero to be very, very proud of."
Another of his colleagues at that age group, Jack Whatmough, helped Portsmouth to a 1-1 draw with Wycombe Wanderers in League Two – the defender being replaced at half-time with the score still goalless.
And U18 goalkeeper Freddie Woodman was an unused sub for Hartlepool United as they went down 2-0 at Plymouth Argyle.
