The 29-year-old has won 16 caps for his country, the last of which came in the 3-0 victory over Latvia in November 2013.
However, a lack of first-team football at Sunderland saw him left out of the pre-World Cup friendlies as David Forde was preferred and Rob Elliot was handed an international debut.
A move to Sheffield Wednesday has seen Westwood return to form, with just one goal conceded in three Championship matches this term.
That has led to a recall from manager Martin O'Neill, with Westwood one of four goalkeepers named in a provisional 36-man squad for the matches at the start of September.
The home meeting with Oman on September 3 is a warm-up for the serious business of Euro 2016 qualifying, which begins in Tbilisi against Georgia four days later.
O'Neill will be without Richard Dunne following the experienced defender's retirement last month, while Stephen Ireland remains out of favour despite the manager previously admitting he had contacted the midfielder over a return.
Ireland have been drawn in Group D with Germany, Scotland, Poland, Gibraltar and Georgia.
Squad in full:
Goalkeepers: Rob Elliot (Newcastle United), David Forde (Millwall), Darren Randolph (Birmingham City), Keiren Westwood (Sheffield Wednesday).
Defenders: Seamus Coleman (Everton), Damien Delaney (Crystal Palace), Shane Duffy (Everton), Stephen Kelly (Reading), Richard Keogh (Derby County), Paul McShane (Hull City), Joey O'Brien (West Ham), John O'Shea (Sunderland), Alex Pearce (Reading), Marc Wilson (Stoke City).
Midfielders: Robbie Brady (Hull City), Ciaran Clark (Aston Villa), Darron Gibson (Everton), Jeff Hendrick (Derby County), James McCarthy (Everton), James McClean (Wigan Athletic), Aiden McGeady (Everton), David Meyler (Hull City), Anthony Pilkington (Cardiff City), Stephen Quinn (Hull City), Andy Reid (Nottingham Forest), Stephen Ward (Burnley), Glenn Whelan (Stoke City).
Attackers: Simon Cox (Reading), Kevin Doyle (Wolves), Wes Hoolahan (Norwich City), Robbie Keane (LA Galaxy), Shane Long (Southampton), Daryl Murphy, Conor Sammon (both Ipswich Town), Anthony Stokes (Celtic), Jon Walters (Stoke City).
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