Former Exiles fly half, Everitt, joined in January 2000 and to this day remains the club's record points scorer with 1,762 points in 169 appearances. He was part of the 2002 Powergen Cup winning side along with new forwards coach, Glenn Delaney.
Everitt said: "I enjoyed seven years as a player at London Irish and I'm thrilled to be returning to the club in a coaching capacity. Tom Homer is an outstanding talent and has a tremendous kicking game as do new recruits Ian Humphreys and Shane Geraghty. I look forward to working with the guys when I join."
Richards first joined London Irish as a development player in July 1996 and made 28 senior appearances before leaving at the end of the 1998-99 season. He went on to represent Harlequins, Bristol Rugby, Benetton Treviso, London Wasps and Gloucester Rugby before returning to Sunbury in 2007.
He was first involved in the senior England set-up in 1998 and went on to play 13 tests. He made his full international debut on the tour of Australia in 2006 and then played in all four of the 2006 Investec Challenge Internationals, including starting both tests against South Africa. Peter made the 2007 World Cup squad and was among the replacements for all seven matches, coming on in six of them including the final.
Richards said: "I am delighted to be returning to London Irish. It is where it all started for me as a player and the springboard for my career. I'm looking forward to working with the scrum halves and helping to develop their games further."
London Irish Director of Rugby, Brian Smith said: "Barry and Peter have been great performers for London Irish during their careers and it is great they are joining our coaching set-up. Barry had a superb kicking game as a player and the fact that he is still the London Irish record points scorer is testament to his quality and hard work. He will be working with our kickers to offer guidance and advice.
"Peter will be working with our scrum-halves on a one-on-one basis to again provide advice and guidance to ensure player development. It is great to have two former players of Barry and Peter's calibre back on board."