Talks to sign up retailers to the Rushden Lakes development could get under way in the coming months.
Despite being given approval by the secretary of state for communities and local government Eric Pickles, there is still a six-week window for this to be appealed against.
But if no appeal is lodged, work can then start on finding retailers to sign up to the Rushden site.
Gavin Stollar, speaking on behalf of LXB Retail which is behind the plans, said: “In terms of the next steps, there are a few legal process hurdles to go through over the coming couple of months.
“Not least the judicial review period that follows a resolution to grant from the secretary of state so we need to wait and see.
“Nothing’s going to happen in the next couple of months until that has passed.
“If there’s a challenge then there will be a legal process that follows.
“But not withstanding that, we then have the opportunity once that period is clear to go out in the market and start talking in a meaningful way to possible operators.
“Marks & Spencer are committed to the scheme which is a great start and a great anchor for the development.
“So there will be a process of formalised marketing and engagement with various different retailers about who we can bring to the site.”
Mr Stollar said he would expect to see more formal announcements about the site off the A45 near Rushden being made in the autumn.
LXB bought the 244-acre site back in 2011 and East Northamptonshire councillors voted unanimously to grant planning permission in October 2012.
But the decision went for review at a public inquiry last July.
Mr Pickles was due to make his decision in February, but several delays resulted in supporters having to wait until early June to find out if they had won their fight.