The Brazilian pair could feature against the Romanians at Stamford Bridge, with Jose Mourinho's men knowing a win would secure top spot in the standings and a more favourable last-16 draw, after recovering from recent injuries.
Luiz has not played for Chelsea since the November 2 loss at Newcastle after returning from international duty with Brazil with a bruised knee, while Oscar suffered an ankle injury in the win over Southampton on December 1.
Ashley Cole, who, like Luiz, has not played since the Newcastle defeat, after which Mourinho was scathing of his players, was also in training after being an unused substitute in recent weeks, with Spain right-back Cesar Azpilicueta preferred at left-back.
Chelsea lost 3-2 at Stoke on Saturday, but beat Steaua 4-0 in Romania at the start of a run of six wins in six games in October.
Steaua are out of contention in Group E, with third-placed Schalke hosting Basle in the night's other match.
Basle, who beat Chelsea twice in the group phase, must avoid defeat to join the Blues in the next phase.