They are joined by Churchill Cup team-mates Paddy Wallace, Jamie Heaslip and Matt McCullough, who have already been part of previous Ireland squads.
O'Sullivan said, "The Churchill Cup has opened up other possible options, so we felt it was worth bringing some of the players into the senior set-up to take a closer look at them and monitor their progress."
Ireland also welcome back some experienced players who missed the summer tour due to injury, with Simon Easterby, Frankie Sheahan, Eoin Reddan and John Kelly all returning.
But O'Sullivan will be without the likes of Gordon D'Arcy, Malcolm O'Kelly and John Hayes, who are all injured.
O'Sullivan added: "While this camp allows us to look at our options, there are some players who toured New Zealand and Australia during the summer who are not part of this training camp, but this does not mean that these players will not be considered or figure in the autumn internationals."
Ireland play South Africa and Australia on successive weekends in November.
R Best (Ulster), N Best (Ulster), Bracken (Wasps), Court (Ulster), Easterby (Llanelli), Fogarty (Connacht), Gleeson (Leinster), Heaslip (Leinster), Horan (Munster), Leamy (Munster), McCullough (Ulster), O'Callaghan (Munster), O'Connell (Munster), M O'Driscoll (Munster), Quinlan (Munster), Sheahan (Munster), D Wallace (Munster), Young (Ulster); Boss (Ulster), Bowe (Ulster), Dempsey (Leinster), Duffy (Harlequins), A Horgan (Munster), S Horgan (Leinster), Hickie (Leinster), Kelly (Munster), Murphy (Leicester), Brian O'Driscoll (Leinster), O'Gara (Munster), Reddan (Wasps), Staunton (Wasps), Stringer (Munster), Trimble (Ulster), Wallace (Ulster).