Public Power Corp. (PPC) is selling the plants in northern Greece and on the southern Peloponnese under the terms of Athens' latest international bailout after an EU court ruled that PPC had abused its dominant position in the coal market.
The bid deadline has been repeatedly pushed back since the tender was launched last year for different reasons.
The Commission has approved a Jan. 23 deadline, an energy ministry official told Reuters on condition of anonymity.
The new deadline gives PPC time to conclude a voluntary redundancy scheme, including about 1,400 people employed at the plants.
PPC, which is 51 percent state-owned, and the energy ministry are handling the divestment and the European Commission is overseeing the process.
PPC has shortlisted six investors, but a source familiar with the matter has said only three may submit binding bids.