O'Callaghan, who became Munster's most-capped player this season, lined out for Ireland against the Baa Baas at Thomond Park four years ago and also at Kingsholm in May 2012.
Back rower Wilson is one of the players included who ended the season competing for silverware. He featured at number 8 for Ulster in last week's RaboDirect PRO12 semi-final loss to Leinster.
The cosmopolitan 24-man squad to face an England XV next Sunday afternoon boasts more than 700 international caps, with O'Callaghan's former Munster team-mate Julien Brugnaut from France another notable inclusion.
A dozen players have been added to the initial Barbarians group, including Ireland lock O'Callaghan, France out-half Francois Trinh-Duc, South African second row Juandre Kruger and Argentina full-back Juan Martin Hernandez.
Nine different nations are represented - six New Zealanders joined by players from Argentina, Australia, France, South Africa, Georgia, Ireland, Samoa and Tonga - and 19 players are set to wear the famous black and white hooped shirt for the first time.
"It's a privilege to be able to work with a group who have achieved so much and we're looking forward to taking on a young England side at Twickenham next Sunday."
There is one change to the group of players previously announced with Castres-bound All Black Sitiveni Sivivatu now unavailable.
Tickets for Sunday's England XV v Barbarians match (Twickenham, kick-off 3pm) are available to purchase here. The game will be broadcast live on Sky Sports 1.
BARBARIANS Squad (v England XV) - Backs (10): Jimmy Cowan (Gloucester/New Zealand), Tomas Cubelli (Belgrano/Argentina), Hosea Gear (Toulouse/New Zealand), Juan Martin Hernandez (Racing Metro 92/Argentina), Brock James (Clermont Auvergne), James O'Connor (London Irish/Australia), Rene Ranger (Montpellier/New Zealand), Joe Rokocoko (Bayonne/New Zealand), Benson Stanley (Clermont Auvergne/New Zealand), Francois Trinh-Duc (Montpellier/France).
Forwards (14): Julien Brugnaut (Racing Metro 92/France), Schalk Ferreira (Toulouse), Mamuka Gorgodze (Montpellier/Georgia), Andrew Hore (Highlanders/New Zealand), Juandre Kruger (Racing Metro 92/South Africa), Alexandre Lapandry (Clermont Auvergne/France), Juan Manuel Leguizamon (Lyon/Argentina), Nahuel Lobo (Montpellier/Argentina), Donncha O'Callaghan (Munster/Ireland), Ti'i Paulo (Clermont Auvergne/Samoa), Sona Taumalolo (Perpignan/Tonga), Joe Tekori (Toulouse/Samoa), Roger Wilson (Ulster/Ireland), Davit Zirakashvili (Clermont Auvergne/Georgia).