The hosts led 26-0 at half-time, with all four of their early tries seeing support play to the fore as they punished Newcastle on almost every incursion.
Scarlets broke the deadlock 14 minutes in when fly-half Sam Costelow ghosted through the middle of a heap of bodies, darting 20 metres between the posts before converting his own try.
They added a second just after the quarter mark when a cross-field kick to the right was offloaded back infield to Fletcher Anderson, with the supporting No.8 powering over from close range.
Costelow’s conversion bounced back off the right post, but they extended their lead on 27 minutes when a midfield line-break enabled former Newcastle centre Johnny Williams to score against his old club as the Welsh international was rewarded for a super support line.
Gareth Davies took their first-half tally to 26 when the scrum-half supported yet another line-break, the Welsh international on the end of a move which went through three pairs of hands before finding him for a simple run-in.
It took the TMO to deny Scarlets a fifth try two minutes into the second half when play was pulled back for a forward pass – neither side putting much together by way of fluency in a scrappy start to the final 40.
The video ref was again to the fore when Obi Ene’s claim for a Newcastle try was chalked off due to a knock-on in the build-up, and the Scarlets rapidly seized back the momentum.
Red Bulls prop Murray McCallum was sent to the sin bin for pulling down a maul near his own line, and the home side were ruthless in making the extra man count.
Ellis Mee was the first to utilise the extra space when the Welsh international caught a long, looping pass for a score in the right corner, and he was followed just two minutes later when Macs Page marked his 50th appearance for the Scarlets with a converted score down the same side of the field.
The pain kept on coming for Newcastle, Page diving over for his second try on 65 minutes when he was quickest to the loose ball following a break down the right and a diagonal in-field kick.
The Red Bulls found some spirit ten minutes from time when Benitez Cruz’s quick tap penalty was worked wide for fellow replacement Oli Spencer to dive in – Josh Hodge adding the conversion from the left touchline.
Ollie Leatherbarrow crashed over for their second try three minutes from time as he worked a back peel from a lineout in the right corner, but the result by that stage was long gone.
Scarlets: 15 Blair Murray, 14 Ellis Mee, 13 Joe Roberts, 12 Johnny Williams (Eddie James, 43), 11 Macs Page, 10 Sam Costelow (Joe Hawkins, 37), 9 Gareth Davies (Dane Blacker, 62); 1 Kemsley Mathias, 2 John McKee (Ryan Elias, 49), 3 Harri O’Connor, 4 Harvey Cuckson (Taine Plumtree, 40), 5 Alex Groves, 6 Sam Lousi (Dan Davis, 63), 7 Josh Macleod (captain), 8 Fletcher Anderson.
Scorers - Tries: Sam Costelow, Fletcher Anderson, Johnny Williams, Gareth Davies, Ellis Mee, Macs Page 2. Conversions: Sam Costelow 2, Joe Hawkins 4.
Newcastle Red Bulls: 15 Josh Hodge, 14 Obi Ene, 13 Chris Harris (Oli Spencer, 54), 12 Cameron Hutchison, 11 Brandon Jackson, 10 Jake Dalziel (Brett Connon, 48), 9 James Elliott (Simón Benítez Cruz, 40); 1 Tom West (Adam Brocklebank, 51), 2 Ollie Fletcher (Samson Adejimi, 51), 3 Francisco Moreno (Murray McCallum, 51), 4 Finn Baker (Oscar Usher, 70), 5 Franco Molina, 6 Allan Ferrie (Max Hicks, 25), 7 Ollie Leatherbarrow, 8 Sam Graham (captain).
Scorers - Tries: Oli Spencer, Ollie Leatherbarrow. Conversions: Josh Hodge 2.
Referee: Evan Urruzmendi (France).
Attendance: 5,692.