The 18-year old midfielder is currently out on loan with Coca Cola League One side Sheffield Wednesday and has impressed during his two month stint at Hillsbrough.
O'Brien made his senior Wanderers debut earlier on this season when coming on as a late substitute in the Carling Cup win over Yeovil Town. He is said to have a bright future with Bolton and this news will no doubt have further enhanced his growing reputation.
Ireland coach Don Givens has named an 18-man squad for the game in Alchchete.
Republic of Ireland U21 squad
Henderson (Notts County), Deeney (Notts County), Brennan (Newcastle United), Kelly (Tottenham Hotspur), Fitzgerald (Bury), Foley (Luton Town), Kohlmann (Borussia Dortmund), Painter (Birmingham City), Flood (Manchester City), Potter (Liverpool), Whelan (Sheffield Wednesday), O'Brien (Sheffield Wednesday), Thorton (Sunderland), Tabb (Brentford), Yeates (Tottenham Hotspur), McAlliskey (Huddersfield Town), Mehmet (Dunfermline Athletic), Bell (Rushden and Diamonds).