Iniesta provided assists for Lionel Messi's quickfire double - his 81st and 82nd goals this calendar year - before lashing home a goal of his own and playing in Cesc Fabregas for a fourth as Barcelona ran riot in a devastating 18-minute spell at the start of the second half.
Jose Barkero had the chance to pull a goal back for the hosts late on but saw his tame penalty saved by Victor Valdes as Barca comfortably maintained their three-point lead at the top of La Liga with their 11th win in 12 matches.
Atletico Madrid stretched their 100 per cent record at the Vicente Calderon this season to 10 games with a comprehensive 4-0 victory over nine-man Sevilla.
The game was almost over as a contest after just 20 minutes when Koke was brought down by Federico Fazio inside the area and - after the Italian defender had seen a red card for a professional foul - Radamel Falcao hammered home his 14th goal of the season from the penalty spot.
Two goals in four minutes just before half-time sealed the points for Atleti as Emir Spahic turned Arda Turan's cross into his own net before Koke capped a fine individual display with a stunning volleyed finish from Diego Costa's lobbed pass.
And Sevilla's miserable night was rounded off when Ivan Rakitic received a second yellow card for hacking down Tiago, leaving Miranda to tap home a fourth goal in stoppage time.
Deportivo moved out of the Primera Division relegation zone thanks to a vital point earned from a draw with Athletic Bilbao at San Mames.
The hosts took a deserved lead before the break as Oscar de Marcos converted Markel Susaeta's cross in the 24th minute, but Abel Aguilar headed Depor level from Juan Carlos Valeron's driven ball just after half-time.
Athletic pressed for the winner but Fernando Llorente failed to find the target with three headers, with Andoni Iraola and Iker Muniain also coming close, and there was to be no way through for the Basque outfit.
Getafe heaped more misery on Espanyol by inflicting a 2-0 defeat on the Primera Division's bottom team at the Estadi Cornella-El Prat.
Pedro Leon's early strike set the visitors on their way and Mane put the result beyond doubt with a second goal in stoppage time.
The result left the Barcelona team rooted to last place while Getafe climbed provisionally to seventh in the standings.