Connor Goldson and Fashion Jr were both on target early in the match, before a James Tavernier penalty gave Rangers a 3-0 advantage at the break. Kilmarnock got a goal back in the second-half through Jeriel Dorsett, but it was Michael Beale’s side who secured the three points at Ibrox.
The Gers boss named four changes to his team from last week’s match at Hampden with Nicolas Raskin, Todd Cantwell, Ryan Jack and Antonio Colak coming into the starting XI in place of John Lundstram, Malik Tillman, Glen Kamara and Alfredo Morelos.
That meant Rangers started at Ibrox with Allan McGregor in goal and a back four of James Tavernier, Connor Goldson, Ben Davies and Borna Barisic.
Ryan Jack, Nicolas Raskin and Todd Cantwell were named in midfield, with Fashion Jr and Ryan Kent supporting striker Antonio Colak.
There was a welcome return to the bench for defender John Souttar as he made his return to the matchday squad from an injury picked up in the opening league match of the season at the end of July.
It was Ryan Kent who got the action underway as the Light Blues looked to start positively at Ibrox. With five minutes on the clock Nicolas Raskin lifted a ball into the box in search of Colak but it was defended well by Kilmarnock and was sent out for a Rangers corner.
From the set-piece, Gers managed to find an early breakthrough. Borna Barisic played a short corner which Todd Cantwell directed towards goal but it was blocked by a Kilmarnock body. The rebound was struck by Colak but was again blocked, before defender Connor Goldson, who was still in an advanced position, managed to touch the ball home for the opening goal at Ibrox.
It was a dominant start from Rangers, who almost had a second inside the opening 15 minutes as Ben Davies played a lovely long ball into the path of Fashion Jr. The forward took a well-controlled first touch before striking a powerful shot towards goal but Kilie goalkeeper Sam Walk matched the effort with a good save.
Minutes later Fashion Jr had another fantastic opportunity in front of goal as he met a Ryan Kent cross at the back post but his touch was inches wide of the post.
The early dominance at Ibrox paid off as Gers doubled their advantage in the 25th minute. Todd Cantwell lifted a ball into the box, which was touched into the path of Fashion Jr by striker Antonio Colak and this time the forward made no mistake in finding the back of the net as he guided a right-footed shot into the bottom corner.
In a well-worked move from Rangers, Antonio Colak and Ryan Kent combined in a one-two, with the former getting a strike away at goal from inside the box but it was just high of the target.
At the other end, Danny Armstrong found the run of Rory McKenzie in the box as he drove toward the Rangers goal, but it was defended well by Connor Goldson who blocked the shot.
Rangers were awarded a penalty a few minutes before the break following a VAR check, as a handball was given against Kilmarnock’s Ryan Alebiousu. James Tavernier stepped up to the spot to take the penalty and hit a perfect right-footed penalty with pace beyond Sam Walker for his 50th Rangers spot-kick.
Early in the second-half, Jordan Jones, who came on as a half-time substitute for Kilmarnock flashed a cross across the face of goal but Ash Taylor’s touch was wide of the target.
Kilmarnock had a goal back with half an hour of the match remaining as Jones’ corner was headed into the back of the net by Jeriel Dorsett.
Michael Beale made his first change of the match with 20 minutes remaining as John Lundstram was introduced in midfield in place of Nico Raskin.
Colak had a strike from distance held by Walker as Rangers looked to restore a three-goal advantage in this match before the Croatian was denied by a fantastic save from the Killie goalkeeper shortly after as he got a strong hand to header following a Ryan Kent cross.
Ryan Jack had the ball in the back of the net with two minutes remaining but the linesman raised his flag for offside.
In added time, John Souttar was introduced for his first minutes since injury as he took to the field alongside Ianis Hagi and Scott Arfield in place of Ben Davies, Todd Cantwell and Antonio Colak.
RANGERS: McGregor, Tavernier, Goldson, Davies (Souttar, 90), Barisic, Jack, Raskin (Lundstram, 72), Cantwell (Arfield, 90), Fashion Jnr (Morelos, 83), Kent, Colak (Hagi, 90)
Subs not used: McLaughlin, Kamara, Wright, Devine.
Kilmarnock: Walker, Dorsett (Sanders, 84), Power (Watson, 77), Taylor, McKenzie, Armstrong (Murray, 72), Wright (Stokes, 84), Chambers, Alebiosu (Jones, 46), Doidge, Polworth.
Subs not used: Hemming, Alston, Robinson, McInroy.
Referee: William Collum
Attendance: 49,545