Jeremy and Jane Hooper, who won the chance to run Thame restaurant Eight at the Thatch in a national television competition, have quit after just six months at the helm.
The Hoopers beat seven other couples for the chance to run their own business in the BBC2 series The Restaurant.
Jeremy, a former chef in the Royal Marines, and Jane, who worked with teenagers, took over the running of Eight at the Thatch with the help of celebrity chef Raymond Blanc last November.
The couple had their first child, Joseph, in March and had put in place a team of staff at the restaurant, but a statement released by Mr Blanc and the couple tonight confirmed they had left for good.
Mr and Mrs Hooper said: "We feel very disappointed that this hasn't worked out.
"We feel that we didn't have the chance to make our concept work in the environment of a pub.
"Having said that, we were thrilled to win the prize and we have learned a lot.
"It has not proved possible to continue at Eight at the Thatch, but we have not lost our dream and still plan to start our own restaurant before too long - probably in our home county of Cornwall."
Mr and Mrs Hooper completed a series of challenging tasks before winning the TV series.
At the time Eight at the Thatch opened, Mrs Hooper said: "It hasn't really sunk in yet that this is ours. It's stunning.
"But there's still so much to learn and so much more to running a restaurant than just serving food."
Mr Blanc, who owns the Le Manoir Aux Quat' Saisons restaurant and hotel in Great Milton, chose the Hoopers as the winners of The Restaurant.
He said last night: "Jeremy and Jane worked very hard to make a success of Eight at the Thatch.
"I am happy that we were able to give them this chance and delighted they have gained the experience and the confidence to start a new business.
"The past year has been very rewarding and I have enjoyed working with Jane and Jeremy.
"I would like to congratulate them on the birth of their son Joseph and wish them the very best for the future."
Peach Pubs, founded by Lee Cash and Hamish Stoddart - who were involved at Eight at the Thatch as business consultants, will take over the running of the pub.
A statement issued by the BBC said: "We wish Jane and Jeremy every success in the future. Their flair and commitment made them admirable winners of the first series."
Filming for a second series of The Restaurant begins shortly. It is due to be shown in the autumn.