Protesters opposed to plans for 15,000 new homes at Weston Otmoor near Bicester may find out on 21 July if their campaign has been successful.
The government is due to announce on that date which eco-town sites are its first choices.
Weston Otmoor site was rated low in a sustainability study and would only be suitable with "substantial and exceptional innovation", it said.
Consultation on 13 sites nationwide finished at the end of April.
The Conservative Party has criticised the plans with shadow housing minister Grant Shapps calling for the "unpopular" scheme to be scrapped.
He told the House of Commons that the "small print" of the Government's draft legislative programme, published last week, showed plans for eco-towns had now been "pushed back to 2020".
Mr Shapps added: "So will the minister, the fourth who has been across the despatch box from me, now just admit that this programme is a shambles?"
Developers were "running scared", the scheme had been delayed by judicial reviews and the plans required "massive public subsidy at a time when the coffers are bare".
But Housing Minister John Healey called on MPs to be patient.
"I've said to the House that I expect to make an announcement before the recess. I haven't finished four weeks of the job at the moment."
Eco-towns would help meet the need for new affordable homes and would be environmentally friendly, he said.
The House of Commons rises for its summer recess on 21 July.