The four board members stood down ahead of a review of services at Southern Health NHS Foundation Trust, which is due to be published next week.
The trust came under fire after Connor Sparrowhawk drowned at its Slade House facility in Oxford.
Its boss Katrina Percy resigned in October amid public pressure.
Previous interim chairman Tim Smart also stood down after he was criticised for creating a new job for Ms Percy.
Current interim chairman Alan Yates, said: "The trust leadership will need to look quite different if it is to meet the needs of patients and service users, as well as its stakeholders.
"Four non-executive directors have this week jointly offered their resignation from their posts so that the governors can, with my help, recruit to the need for all five new non-executive directors."
Mr Yates, previously the trust's improvement director, said the trust would also need to find a new chairman before he leaves in July.
The review looks at the trust's mental health, learning disability, and community physical health services.
"The board has identified the benefits of much greater inclusion of service users and carers in the organisation as well as the delivery of its services," Mr Yates said.
July 2013 - Connor Sparrowhawk, 18, drowns after an epileptic seizure at Oxford unit Slade House. An inquest later rules neglect contributed to his death
11 December 2015 - The BBC reveals details of a leaked Mazars report which highlights a "failure of leadership". Health Secretary Jeremy Hunt says he is "profoundly shocked"
17 December 2015 - The report is officially published and shows out of 722 unexpected deaths over four years, only 272 were properly investigated
6 April 2016 - The Care Quality Commission (CQC) issues a warning notice to significantly improve protection for mental health patients
29 April 2016 - A full CQC inspection report is published, which says the trust is continuing to put patients at risk
30 June 2016 - Following a review of the management team competencies, it is announced that Katrina Percy is to keep her job
29 July 2016 - The BBC reveals the trust paid millions of pounds in contracts to companies owned by previous associates of Ms Percy
30 August 2016 - Ms Percy announces she is standing down as chief executive, but is staying on in an advisory role
19 September 2016 - Interim chairman Tim Smart resigns after admitting he created a job for Ms Percy
7 October 2016 - Ms Percy resigns completely from the trust

The five-time African champions have been draw in a pool with SuperSport United, Horoya and Mounana in the expanded group stage.
Three-time winners CS Sfaxien of Tunisia will face South Africa's Platinum Stars, debutants Mbabane Swallows of Swaziland and Mouloudia Alger from Algeria.
Moroccan side FUS Rabat, who won the tournament in 2010, face two sides making the debuts in the group stages in Rivers United of Nigeria and Uganda's KCCA.
The group is completed by Tunisia's Club Africain, who were crowned continental champions in 1991 and runners-up in this competition 20 years later.
Rivers United were the last team to qualify for the group stage with a 2-0 aggregate win over Rayon Sports after a goalless draw in Rwanda on Saturday.
The first leg of the tie was postponed due to the the commemorations for the genocide in Rwanda.
First group matches due to be played on the weekend of 12-14 May.
The top two from each group will progress to the quarter-finals with the final set to be played over two legs in November.

The Common dolphin was discovered on the high water line at Gyllingvase near Falmouth early on Wednesday.
Members of British Divers Marine Life Rescue covered the animal with wet towels and seaweed to keep it comfortable.
A vet who was called to the scene assessed that it was too sick to be returned to the sea.
There have been 41 strandings of Common dolphins in Cornwall in the past year according to figures from the Marine Strandings Network.
Almost 3,500 whales, dolphins and porpoises have been stranded on UK coastlines over the six years up to December 2011, according to the Zoological Society of London (ZSL).
Overall it recorded a fall in the number of strandings but said that some still were not being reported.
The Society has launched a campaign to encourage the public to tell them when they find beached mammals.
All the non-executive directors of an NHS trust criticised for failing to properly investigate hundreds of deaths have resigned.
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TP Mazembe of DR Congo face trips to South Africa, Guinea and Gabon as they bid to defend their Confederation Cup title.
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A dolphin found stranded on a Cornish beach has been put down, say marine rescuers.