Miguel Almirón's composed finish sent the Magpies ahead in the opening stages of a testimonial match in honour of former Gers goalkeeper Allan McGregor, who made over 500 competitive appearances in two spells at the Scottish Premiership outfit.
Rangers equalised shortly after the hour mark through Sam Lammers' strike, as the Dutchman dispossessed Bruno Guimarães before Ashby scored his first goal for the club since joining from West Ham United in January 2023, guiding the ball home from Alexander Isak's impressive cross in the final stages.
Eddie Howe made seven changes from the side which claimed a 3-2 comeback victory against National League side Gateshead on Saturday as Sandro Tonali was handed his highly-anticipated Magpies bow following his transfer from AC Milan earlier this month.
Newcastle began the friendly encounter in positive fashion, with Almirón latching onto Jamal Lewis' cross into the penalty area but the South American winger, who scored 11 Premier League goals for United last season, was unable to fire an attempt towards goal.
However, in the 16th minute, Almirón broke the deadlock for the visitors after completing a neat attacking move as Tonali and Elliot Anderson combined with a delightful one-two before the latter teed up the Paraguayan forward who placed a low first-time effort into the bottom left-hand corner.
Newcastle controlled the majority of possession in the first-half, with the hosts unable to create a meaningful shot on target, with Lammers' tame effort from the edge of the box comfortably held by the German shot-stopper before Kieran Dowell lashed a low effort wide of the target.
Newcastle went in search of a second goal of the evening as Tonali's diagonal pass flew towards Kieran Trippier on the right flank before the full-back picked out Almirón, who could only loop the ball over McGregor's crossbar.
Before the conclusion of the opening 45 minutes, Todd Cantwell failed to draw the Gers level after latching onto Dowell's forward pass but the former Norwich City midfielder dragged a low effort wide of the far right-hand post.
Seven substitutions were made before the restart, with the likes of Guimarães, Isak and Anthony Gordon introduced to the field while a further four were made shortly after the hour mark, including Paul Dummett who was making his first Magpies appearance since August - a Carabao Cup victory against Tranmere Rovers.
In the 64th minute, Rangers drew level through Lammers as the Dutch forward intercepted Karl Darlow's intended pass to Guimarães before slotting the ball beyond the 32-year-old goalkeeper.
Newcastle went in search of regaining their lead as Guimarães' curling free-kick was inadvertently flicked towards goal by Gers substitute Ianis Hagi but Jack Butland, replacing the long-serving McGregor, held the goal bound header.
In the 87th minute, Newcastle took the lead as Ashby recorded his first goal for the Magpies. After Isak raced onto Dan Burn's forward pass, the Swedish striker advanced dangerously into the box before directing an inviting cross into the path of Ashby who, in front of the 8,000 travelling away supporters, guided the ball into the right-hand corner.
Darlow was on hand to prevent Rangers netting a stoppage-time equaliser, getting down low to importantly push away Alex Lowry's low drive from the edge of the box.
Newcastle United: Loris Karius (Karl Darlow 46), Kieran Trippier (c) (Javier Manquillo 46), Fabian Schär (Paul Dummett 62), Sven Botman (Dan Burn 46), Matt Targett (Anthony Gordon 46), Sean Longstaff (Lewis Miley 46), Elliot Anderson (Alex Murphy 62), Sandro Tonali (Bruno Guimarães 46), Miguel Almirón (Joe White 62), Jamal Lewis (Harrison Ashby 62), Callum Wilson (Alexander Isak 46)
Subs not used: Mark Gillespie, Jay Turner-Cooke, Ben Parkinson
