Long has been unstoppable since the turn of the year and took his tally to 20 for the season with the opening goal as Brian McDermott's side closed to within six points of the top six.
The Irishman has now scored 12 times in his last 15 games for Reading and will pose a threat for Manchester City when the sides meet in this weekend's FA Cup quarter-final clash.
The win was wrapped up in the last five minutes by veteran Ian Harte's trademark free-kick and a Noel Hunt finish which added a touch of gloss to a fine performance, leaving Connor Wickham's goal in stoppage time a consolation.
The hosts were without midfielder Jimmy Bullard - who scored both goals in the win at Cardiff at the weekend - and his presence was sorely missed as Reading took charge.
Jason Scotland saw his low shot easily saved by Alex McCarthy before the visitors were forced into an early change as captain Matt Mills limped out to be replaced by Ivar Ingimarsson.
The loss of Mills - who scored the winner at Everton last week - had the potential to upset the Royals but instead they took the lead moments later through Long's 18th-minute strike.
Brian Howard swept in a corner from the left and Long stole in ahead of his marker to flick in a header at the near post and register his 20th goal of the season.
Ipswich midfielder Grant Leadbitter went close with an audacious effort after he flicked up a free-kick and crashed a 25-yard volley just over the top but it was Long who ended the half in style.
The Republic of Ireland international received the ball with his back to goal but rolled his marker Gareth McAuley brilliantly to send in a low drive which Marton Fulop did well to keep out.
The home side were quick out of the blocks at the resumption with Andy Drury lashing over the crossbar but again it was Long who almost found a way through.
Long controlled a long ball on his thigh before bursting clear of the defence and testing Fulop with a powerful strike. Jem Karacan was first to the loose ball and found Howard but the midfielder screwed his shot wide.
Scotland was replaced by Tamas Priskin as Paul Jewell searched for an answer and McAuley went close with a header from a corner but Harte killed the game off with his 82nd-minute strike.
Hunt was fouled some 30 yards from goal but the former Leeds left-back curled an unstoppable shot into the top corner.
Hunt then got on the scoresheet with a minute left, breaking a weak challenge in midfield and scampering away to round Fulop and tap into an empty net.
Wickham completed the scoring in added time with a low shot from a tight angle after Leadbitter found a way through.