Missing the out on loan Evan Towler and Ryan Duncan along with suspended duo Findlay Marshall and Alfie Bavidge, Kai Watson made a debut at right back while there was another start for 15 year old Cammy Wilson.
The hosts meanwhile started with several players who have enjoyed Lowland League experience with the Gers B team this season.
It was the worst possible start to the game for Aberdeen as Rangers took the lead within the first minute, good work on the right from Ure seeing Rory Wilson getting the final touch from six yards to find the net.
The Dons weathered some early pressure from the hosts and drew level on 16 minutes, Blair McKenzie's powerful header from Dylan Lobban's corner leaving the keeper helpless.
Rangers enjoyed the bulk of possession, but the Dons were keeping their shape well and chances were at a premium. However, it took a fin block at the edge of his area from Blessing Oluyemi to deny the dangerous Ure just beyond the half hour mark.
A sclaffed effort from centre back Allen found the bottom corner of the net following a corner to give the Light Blues the lead, a real body blow to the Dons.
They reacted well though and a searing break from the pacy Adam Emslie saw him pick out Liam Harvey, only for a brave block from Allan to deny the striker an equaliser. Just on the interval, Harvey broke clear but just couldn't find Emslie who was in acres of space.
Another tough shift for Barry Robson's battlers but they had shown enough to have the tie still very much alive at the break.
Half time - Rangers 2 Aberdeen 1
Just like the League meeting seven days ago, Rangers were on the mark again within two minutes of the restart, Dunlop playing a deft through ball which was flicked on for Wilson to rifle the ball into the net to make it 3-1.
Oluyemi produced a heroic save at point blank to deny Ure, but on 59 minutes Pasnik put the tie beyond doubt when he pounced on a headed clearance from a Dons goal kick to race forward then cut on to his left foot before striking a fine shot into the bottom corner.
Rangers made a raft of substitutions but Aberdeen enjoyed the best of the last half hour of play, Finn Yeats and Wilson causing the Rangers team plenty of problems as they almost created a first goal at this level for the impressive 15 year old. What he lacks in stature at this tender age, he more than compensates for in commitment and skill. Definitely one to watch over the coming months and years.
Try as they might the Dons couldn't get the second goal their play and endeavour deserved so Rangers avenged their semi final defeat two years ago to the Dons to take their place in this season's last four.
Next up for the Dons is a return to Cormack Park next Friday to face Hearts on League duty, kick off at 6pm.
Reaction | Barry Robson
"I was proud of the boys tonight.
"I know people will look at the score and think that is a strange thing to say but we were very very young tonight. We had some players out there who were two or three years younger.
"The pleasing factor was the players followed the instructions we gave them all week.
"We adapted our game plan slightly, we sat off them a bit more and then encouraged certain players to go and put pressure on the ball. I thought we did it well and we looked a threat on the counter.
"Ultimately the power, pace and experience of the Rangers players was just too much.
"50 minutes in, we were very much still in the game, and I know how fit our players are, but they don't have the same size and we got overpowered. At this age group two or three years difference is massive in terms of their physical development. Many of their players have played for their B team.
"We had players missing whilst Rangers took back their loan players and B team players.
"We took younger ones up and gave them a chance to play at a higher level so they can get more experience and get better. Cameron Wilson and Kai Watson deserve a special mention for the way they performed.
"As we always have said we already have one eye on next season. We knew this season would be difficult. We knew we would win some and lose some. Next year it will be very different, we will be strong and all these boys will have had a year's experience at this level and hopefully we can get back to the final stages of this competition."