James McFadden threatened to take the limelight away from Newcastle's victory with a cheeky penalty attempt near the end of the game, but the Magpies eventually overpowered their Scottish counterparts and ran out comfortable winners.
The 48-time capped Scotland forward is out of contract with Well but is close to agreeing a new deal, and appeared against Alan Pardew's men as a second-half trialist.
By the time of his arrival, however, his team were already behind to goals from Haris Vuckic, Yoan Gouffran and Moussa Sissoko, with just Iain Vigurs' opportunistic strike to show for their first-half efforts.
McFadden soon reduced the deficit with a clever penalty but the youthful Magpies outfit again showed their class with a fourth from substitute Sylvain Marveaux as they wrapped up a comfortable win.
The home side started without new signing Stephen McManus but did include seven-time capped Estonian international Henri Anier as a trialist, while Newcastle featured former St Mirren loanee Paul Dummett in defence.
The Barclays Premier League side took just eight minutes to strike as Well keeper Lee Hollis blocked at the feet of Gouffran but left his net unguarded for playmaker Vuckic to slot into from the rebound.
The hosts then backed off as the Slovenian returned the favour by playing in to Gouffran to fire under Hollis again on the quarter hour
Against the run of play, Motherwell pulled a goal back on 26 minutes when Vigurs drilled a low effort past the stationary Robert Elliot from 18 yards, but Pardew's side restored their two-goal lead before the break when Sissoko evaded a tackle with a neat flick before Hollis allowed a meek shot to squirm under his body.
The goalscorer, however, was at fault as Motherwell struck again when he tugged down Stuart Carswell in the box seven minutes after the restart.
McFadden chipped his penalty straight down the middle, but the act of ingenuity mattered little as Marveaux netted a fourth for the Englishmen on 65 minutes from Dummett's pin-point low cross to the back post.