The World Cup winner inspired the visitors to victory, crashing a quickfire half century and also taking two for 21 from four tight overs.
Moeen's 52 from 30 balls included three fours and four sixes, and helped the Rapids to 185 for seven, which proved too many for the Steelbacks.
A careless batting performance from the top order saw the Steelbacks reduced to 52 for four, and with Moeen and New Zealand leg-spinner Ish Sodhi tyings things up in the middle overs, the home side were never seriously in the chase.
An excellent 36 from 21 balls from Saif Zaib including five successive fours off one Josh Tongue over, briefly raised hopes, but once he was run out it was all over to leave the fans allowed back into the ground for their first T20 action since 2019 disappointed.
The Steelbacks won the toss and started the game well, with Sanderson striking with the final ball of the second over.
The seamer started with a wide, and chucked in another, but he got his radar right as he bowled former Northants man Riki Wessels, regularly a thorn in the Steelbacks' side, through the gate.
That left the Rapids 11 for one, and in the next over Wayne Parnell had what looked a good shout for leg before against Moeen turned down, and the England man then hit the first boundary of the match to rub salt in the wounds.
The powerplay ended with the Rapids on 36 for one, but that was the signal for the visitors to up the run-rate.
Brett D'Oliveira hammered Graeme White over wide mid-on for the first six of the match in the seventh over, and repeated the trick a few balls later off Tom Taylor.
Moreen then got in on the act in the ninth, hitting former team-mate Parnell for a four and two sixes - the second of which was a lucky top edge that went all the way over the third man boundary.
The Rapids had hit 41 in just three overs, and they weren't stopping there.
The fours and sixes kept on coming as Rapids raced to 105 for one in the 11th over, but the breakthrough came as Moeen, who had just brought up his 50 with a towering six over mid-wicket, sent a White delivery down Zaib's throat at deep mid-on.
That brought to an end a partnership of 94 in just 8.5 overs, with Moeen hitting 52 off 30 balls, although the England World Cup winner will have been kicking himself for giving his wicket away.
The Steelbacks bowlers fought dragged things back well, with Tom Taylor in particular impressing, but D'Oliveira (43 off 34) and Ben Cox (26 off 10) kept the boundary count ticking over, and the visitors ended on what looked a competitive 185 for seven,
Sanderson ended with three for 21 from three overs and Taylor thee for 33 from four.
The Steelbacks endured the worst possible start to their reply as Richard Levi middled the first ball of the innings from Josh Tongue straigt to D'Oliveira at point and he held on, although the power of the shot very nearly knocked him over!
It was 16 for two in the third over, Ricardo Vasconcelos going for a big hit over mid-wicket and not getting hold of it, but it still took a stunning catch from Ross Whiteley to dismiss him, diving forward full length to take the ball just inches from the ground.
Adam Rossington and Josh Cobb set about restoring the damage, and Cobb had raced to 29 from just 10 balls when he went for one big hit too many and miscued to mid-on off Charlie Morris to leave Steelbacks 52 for three.
Rapids then introduced leg-spinner Ish Sodhi and he struck a big blow first ball, bowling Rossington who was trying to sweep a ball from his off stump. He missed, and was bowled for 22 to make it 52-4.
Rob Keogh and Parnell steered the Steelbacks to 77 for four at the halfway stage, with the spin of Sodhi and Moeen keping it tight, meaning Northants had a lot of work to do in the second half of the innings.
That work was made all the harder when Parnell was stumped for 11 dancing down the wicket to Moeen, leaving the Steelbacks in all sorts of bother at 86 for five.
Keogh perished in the deep going for a six over deep square-leg, and when Taylor was run out by Moeen after being sent back by Zaib the Steelbacks were 98 for seven in the 15th over.
Left-hander Zaib then did his best to make a game of it, but there was never any serious chance of the Steelbacks threatening the Rapids total as the innings closed on 153 for nine.