Ramires opened the scoring midway through the first half and Chelsea doubled their lead just before the break thanks to a comical Daniel Georgievski own goal.
Another Ramires strike early in the second period put the result beyond any doubt and Frank Lampard added a late fourth as Jose Mourinho's men responded in the ideal manner to a shock home loss against Basel on matchday one.
Juan Mata earned a recall to the starting XI after an impressive performance as a substitute in the 1-1 draw with Tottenham Hotspur, and he was immediately into the action with a neat pull-back for Andre Schurrle to get away a shot which was blocked.
Fernando Torres was again the preferred option up front despite being sent off at White Hart Lane, but he lasted just 11 minutes before leaving the field with a knee injury and being replaced by Samuel Eto'o.
Chelsea kept up the intensity and the closed roof at the National Arena meant there was no reason to have any concerns about the state of the pitch following significant rainfall in Bucharest in the days leading up to the fixture.
Steaua had kept a clean sheet in beating Chelsea in the home leg of their Europa League tie last season but looked vulnerable defensively from the start and it was no surprise when Ramires gave the visitors the lead after just 19 minutes.
Schurrle burst past Georgievski on the left wing before squaring the ball for Eto'o, whose scuffed shot turned into a perfect assist as Ramires reacted quickly to prod in from close range.
Schurrle repeatedly tormented his full-back as Chelsea continued to dominate, although the German winger showed a lack of composure when he blazed a long-range effort over the bar and Oscar also sliced horribly off target from the edge of the area.
The only time Chelsea looked in danger of conceding in the first half was when Oscar failed to find David Luiz with a pass back into defence and Petr Cech had to rush at least 15 yards out of his area to beat Cristian Tanase and kick it clear.
The cushion of a second goal came just before half-time when Eto'o latched on to a clever Mata pass and cut inside his defender before shooting powerfully at goal. Ciprian Tatarusanu made a smart save but ball rebounded straight into the path of the retreating Georgievski and ricocheted into the net.
Steaua made a couple of changes at the interval in a bid to get back into the game but the momentum remained with the Blues and Eto'o was desperate to score his first goal for the club as he forced Tatarusanu into a save from distance.
Chelsea made it 3-0 in the 55th minute and the goal again stemmed from Schurrle, who turned away from the hapless Georgievski with a neat piece of skill before crossing for Oscar. He helped the ball on for Ramires and the midfielder notched his second of the game with a fine finish inside Tatarusanu's left-hand post.
Mata hit the post moments later following a slick move which contained the most exquisite of back-heels by Oscar, while Schurrle was denied by Tatarusanu after another good run down the left.
There was a moment of concern for Chelsea when Petr Cech had to back-pedal quickly to tip a delightful Tanase lob over the crossbar and in the process collided with the post, but the keeper was fine to continue.
The impressive Schurrle fired narrowly wide and Eto'o had a well-struck volley from a tight angle saved.
At the other end Nicolae Stanciu drew a good stop from Cech before smashing the follow-up high, while Cech also had to save athletically from Tanase on another rare foray forward for the Romanians.
Lampard added late gloss to the scoreline with a precise low finish that went in off the post in the 90th minute, on a night when Chelsea got their campaign back on track.