All four were included in Ryan Giggs’ training camp squad in Portugal, the highest number from any club, but the manager has now slimmed the squad down for the qualifying games for the games in Croatia on June 8 and Hungary on June 11.
The Dragons, who reached the semi-finals of the 2016 Euros, won their first game of this qualifying group against Slovakia in March.
The next two weeks will be an opportunity for both striker Moore and left-back Williams to make their international debuts, while they will train alongside Real Madrid superstar Gareth Bale.
Moore, who was born and raised in Devon but has a Welsh grandparent, was given a first call-up after powering Barnsley to promotion from League One with 17 goals from 26 starts and five substitute appearances.
Williams, 20, was selected for the first time after his debut season in professional football saw him play 15 times for the Reds in all competitions. He has previously played youth football for Wales.
Goalkeeper Davies made his debut in the last international break in March. Winger Hedges, 23, had the most caps of all the Barnsley players – with three – but he has been dropped from the final squad.
Meanwhile, four former Barnsley players are part of the England squad which is in Portugal for the Nations League last four. John Stones, who turned 25 on Tuesday, will be hoping to add to his 37 caps in the semi-final against the Netherlands on Thursday then either the final or third/fourth play-off against Switzerland or Portugal.
The Thurlstone man, who came through the Oakwell academy and played 28 first team games from 2012 to 2013, was part of the 2018/19 Manchester City squad who became the first men’s team to win the English domestic treble.
Stones was not in the squad for the League Cup final, following injury, and came off the bench in the FA Cup final last week while he has started 20 of their 38 Premier League games.
Also in Gareth Southgate’s squad are former Barnsley loanees Kieran Tripper – the right-back who looks set to play in the Champions League final tomorrow for Tottenham Hotspur against Liverpool – and goalkeeper Jack Butland who is being linked with a move back to the Premier League after spending a season in the Championship with Stoke City.
Southgate has also selected centre-back Harry Maguire who spent time in the Oakwell academy alongside Stones before leaving when Barnsley went through financial difficulties in the early 2000s.