All four men have been promoted from the Saxons squad as injury replacements for Alex Corbisiero, Rob Webber, Tom Croft and Ben Foden respectively.
Monye is back in the elite fold having not featured for the first team since the 2010 Six Nations. The Harlequins flyer won two Test caps on the 2009 Lions tour but has seen his England chances limited since his return from South Africa.
Haskell had game time in England's most recent Test match against the Springboks during the summer but had previously been out of the fold having opted to play his club rugby in New Zealand and Japan after the 2011 World Cup.
Vunipola is just 21 years old but has been fast tracked into the senior side after an impressive start to the season with Saracens. The 20-stone loosehead's father played at two World Cups for Tonga and the youngster also qualifies for Wales despite having represented England at U18 and U20 level.
Youngs, who is the brother of England scrum-half Ben and is a recent convert from centre, was named in the summer squad for South Africa but didn't make the matchday squads for any of the three Tests against Heyneke Meyer's men.
The 25-year-old's remarkable rise from Championship rugby with Nottingham looks set to continue with a first cap against Fiji at Twickenham on November 10 as Lions hopeful Dylan Hartley is the only other hooker included in the party.
"As a coaching team we can't wait to go into camp and get the guys focused on what will be a massive challenge - Fiji and then the three major Southern Hemisphere teams in successive weeks.
"We have been impressed with some of the rugby we have seen in the Aviva Premiership and Heineken Cup and are looking forward to the players bringing that form to Twickenham," said head coach Stuart Lancaster as his squad get ready to meet up at the Football Association's new St George's Park development in Burton this Sunday.
"It's great to be able to give Mako a chance in the squad. He has come through our age grade sides and made a real impact at Saracens.
"Likewise Tom Youngs, who was with us on tour in South Africa, and we know what James Haskell and Ugo Monye are capable of if they get their opportunity."
England will train at St George's Park through to next Thursday, before returning to their usual training base of Pennyhill Park, in Bagshot on Sunday, November 4.
Backs: Anthony Allen (Leicester Tigers), Chris Ashton (Saracens), Brad Barritt (Saracens), Mike Brown (Harlequins), Danny Care (Harlequins), Lee Dickson (Northampton Saints), Owen Farrell (Saracens), Toby Flood (Leicester Tigers), Alex Goode (Saracens), Jonathan Joseph (London Irish), Ugo Monye (Harlequins), Charlie Sharples (Gloucester Rugby), Manusamoa Tuilagi (Leicester Tigers), Jordan Turner-Hall (Harlequins), Ben Youngs (Leicester Tigers)
Forwards: Mouritz Botha (Saracens), Dan Cole (Leicester Tigers), James Haskell (London Wasps), Phil Dowson (Northampton Saints), Dylan Hartley (Northampton Saints), Tom Johnson (Exeter Chiefs), Courtney Lawes (Northampton Saints), Joe Marler (Harlequins), Ben Morgan (Gloucester Rugby), Tom Palmer (London Wasps), Geoff Parling (Leicester Tigers), Chris Robshaw (Harlequins), Mako Vunipola (Saracens), Thomas Waldrom (Leicester Tigers), David Wilson (Bath Rugby), Tom Wood (Northampton Saints), Tom Youngs (Leicester Tigers)
England's autumn fixtures
v Fiji, Saturday November 10, Twickenham
v Australia, Saturday November 17, Twickenham
v South Africa, Saturday November 24, Twickenham
v New Zealand, Saturday December 1, Twickenham