The Brazilian netted twice either side of a Daniel Georgievski own goal as Jose Mourinho secured his first European win since returning to Stamford Bridge with some ease
Ramires gave Jose Mourinho's side the lead after 19 minutes before Daniel Georgievski's own goal just before half-time gave them breathing space.
The Brazilian then netted his second 10 minutes into the second period before Frank Lampard rounded off the scoring in the final minute to give Chelsea their first points in Group E.
Steaua coach Laurentiu Reghecampf made just one change from Saturday's 3-0 win over Poli Timisoara, with Adrian Popa replacing Gabriel Iancu.
Meanwhile, Mourinho made two alterations to the side that drew 1-1 with Tottenham as Juan Mata and Andre Schurrle came in for John Obi Mikel and Eden Hazard.
The two replacements combined in the fourth minute as Mata found Schurrle inside the area, but his effort was cleared off the line by a covering defender.
However, the visitors were dealt a blow in the 10th minute when Fernando Torres was forced off with what appeared to be a knee injury, to be replaced by Samuel Eto'o.
The early change did little to upset Chelsea, as 10 minutes later Ramires put them in front.
Schurrle broke free down the left before finding Eto'o, whose scuffed effort ran perfectly for the Brazilian to prod home from six yards.
On the half hour, the visitors threatened again, Eto'o and Mata combining on the edge of the box before the latter's weak shot was straight at Ciprian Tatarusanu.
Chelsea were looking increasingly dangerous on the counter, and they duly doubled their advantage a minute before half-time with another rapid break.
Eto'o surged forward before cutting in from the left, with Tatarusanu parrying his effort straight into the path of the onrushing Georgievski, who could do little to avoid diverting the ball into the empty net.
Ten minutes after the break, Ramires got his second and Chelsea's third to put the visitors in total control.
Schurrle turned past his man brilliantly down the left before slipping the ball inside to Oscar, who fed Ramires, the Brazilian taking a touch before firing beyond Tatarusanu.
It was almost a fourth three minutes later, Mata striking the post after collecting Oscar's backheel inside the box.
The hosts responded immediately with their best effort of the game, Cech back-pedalling sharply to tip over Cristian Tanase's chip.
Chelsea were on the offensive again, Schurrle wasting two presentable chances midway through the half as the game became stretched.
There were some signs of life from the hosts in the 73rd minute, Nicolae Stanciu being denied by Cech before blazing the rebound over the bar.
But in the final minute, substitute Willian fed Lampard on the edge of the box, who swept the ball in off the left-hand post to complete an excellent night for Chelsea.