Toon boss Alan Pardew had to change his defence for the first time this season after injuries to Steven Taylor and Fabricio Coloccini.
And Paul Lambert took full advantage of their weakness by going with muscle men Holt and Morison up front.
And the move paid off handsomely as the Canaries strike pairing both netted in this cruise, Holt twice to Morison's single effort.
Newcastle netted twice through in-form Demba Ba but their afternoon ended on a sour note after Dan Gosling was sent off.
Pardew admitted Holt and Morison gave his side a torrid afternoon.
He said: "It's fairly obvious we missed our defenders. Our squad has been stretched to the limit.
"Having three first team centre-halves missing is major. We did very well other than the set plays today.
"Morison and Holt are a handful and so was Wes Hoolahan in behind. They gave us some tough times today.
"We expect to have one or two back next week and we certainly need them.
"We can't concede from three set plays and expect to win the game."
Lambert hailed Holt for stepping straight into the starting line-up having been a sub in the previous four games.
He said: "He's as important as he was two years ago when I joined.
"He and Morison were excellent today. I'm delighted with everyone's contribution."
John Ruddy was into action early on for the home side, saving efforts from Jonas Gutierrez and Yohan Cabaye.
Norwich had weak appeals for a penalty turned down after Andrew Surman hit the deck under the slightest of pressure from Gabriel Obertan.
Norwich had another shout for a penalty declined after 26 minutes when Kyle Naughton's flat cross caught Davide Santon's outstretched arm but again referee Martin Atkinson waved play on.
Only a superb diving save from Ruddy stopped Cabaye giving the visitors the lead with a deflected looping effort from 25 yards.
Norwich hit back, though, and scored five minutes before the break in controversial circumstances. The assistant referee, despite being positioned at least 30 yards away, ruled that Tim Krul had carried the ball out for a corner from a looping shot despite the goalkeeper insisting he had kept the ball in, with replays appearing to back up the Dutchman.
Krul palmed away Andrew Crofts' powerful header from the resulting corner but the ball rebounded in off Hoolahan, with Newcastle's players furious that Atkinson had given the set-piece in Norwich's favour.
But Ba put the away side back in the game in first-half injury-time when he picked up Cabaye's brilliant pass to slip the ball past Ruddy.
Senegalese hitman Ba was left unmarked at the back post immediately after the interval but blazed over from a tight angle.
Hoolahan was booked for kicking the ball away from a Magpies free-kick before Gosling went into the book for a foul on the opening goalscorer soon after.
Norwich made it 2-1 just before the hour when Krul parried Holt's header with his feet before the journeyman striker powered home the rebound off the bar from eight yards.
The goal, Holt's fifth of the season, buoyed the home side and they added their third four minutes later.
Gosling dallied on the edged of his own box, allowing Crofts to race down the flank and cross for Morison, who hammered home a powerful header for his seventh of the season.
Gosling's afternoon went from bad to worse two minutes later when he was given a straight red for a dangerous late tackle on Russell Martin.
The match was set up for a tense finale when Ameobi won the ball on the halfway line after Zak Whitbread dallied and played in Ba, who controlled calmly before drilling past Ruddy with 20 minutes to go.
Obertan then created space with a couple of step-overs but could only fire straight at Ruddy.
Bradley Johnson came on for Surman with 15 minutes left while Sammy Ameobi replaced Obertan for Newcastle.
Newcastle kept up the pressure in search of an equaliser but the tense atmosphere around Carrow Road eased with eight minutes to go as Holt took advantage of slack marking to head home Johnson's cross to kill off the Magpies.
Norwich: Ruddy, Naughton, Whitbread (Barnett 83), Martin, Tierney, Crofts, Fox, Hoolahan (Jackson 84), Surman (Johnson 76) Morison, Holt. Subs not used: Rudd, Pilkington, Bennett, Wilbraham. Booked: Crofts, Fox, Hoolahan. Goals: Hoolahan 39, Holt 59, Morison 63, Holt 82.
Newcastle: Krul, Santon (Ferguson 90), Simpson, Perch, Ryan Taylor, Obertan (Sammy Ameobi 80), Cabaye, Gosling,Gutierrez, Ba, Shola Ameobi (Smith 90). Subs not used: Elliot, Ben Arfa, Lovenkrands, Best. Sent off: Gosling (66). Booked: Shola Ameobi, Gosling. Goals: Ba 45, 71.