Front three Lionel Messi, Luis Suarez and Neymar were also on target for Barca in the second half of a straightforward night for Luis Enrique's men, making it four wins on the spin in all competitions as they finally begin to find some momentum.
Three days after picking up a Copa del Rey win over Real Sociedad, Barca were back in the Basque region but this time they took their time to find their rhythm in the compact 5,500-capacity stadium.
Home boss Jose Luis Mendilibar promised that his side would not sit back against the defending league champions, and he was true to his word as Ander Capa was denied by Marc-Andre ter Stegen with seven minutes on the clock.
The high press was working against Barca, who were also dealt a blow early on when Sergio Busquets was forced off the field to be replaced by Denis Suarez - the man who would go on to score the key breakthrough goal later in the half.
Prior to that, Luis Suarez blasted high over the bar when picked out by a scooped Messi pass from deep, while Ter Stegen was required to block attempts from Gonzalo Escalante and dangerman Pedro Leon in quick succession.
It took until the half-hour mark for the Catalan giants to register their first serious attempt of the match - Messi's free kick from 30 yards out being pushed aside by Yoel, whose next involvement in the match was to pick the ball out of the net.
Substitute Suarez was given time and space to blast a first-time shot into the bottom corner from the edge of the box - his first senior goal in the Blaugrana strip.
Barcelona had a few good chances to extend their lead prior to the interval, with Neymar getting the ball stuck under his feet when through on goal, Arda Turan chesting into the arms of Yoel when spotted by another sublime Messi ball, and Luis Suarez hitting the post from a one-on-one position.
Eibar's hopes of picking up a first league point against their opponents faded soon into the second half, as Messi swept home on the half-volley after Luis Suarez spotted his run with an inch-perfect cross.
A poor clearance from Umtiti allowed Adrian Gonzalez to try his luck from range, sending a shot down the middle for Ter Stegen to easily keep out.
Following a brief spell of pressure from Los Armeros, Barca made sure of the win thanks to a strike from Luis Suarez after getting the better of Florian Lejeune and tucking the ball home at the near post.
That kept up the visitors' impressive average of scoring three goals a game against Eibar across their five meetings, and there was still time for another to arrive in added time.
Pedro Leon and Escalante both came close at one end, only for Ter Stegen to thwart them, allowing Neymar to pick his spot late on to score his first league goal from open play in 12 outings - another magical night for the 'MSN' triumvirate.