Conlan played in Northern Ireland's 1-1 draw against the Czech Republic on Wednesday and last night Gallagher played the full 90 minutes as the Republic of Ireland beat Luxembourg 5-2 in the first of their qualifiers.
The game was played at the Alphonse Theis Stadium in Hesperange, Luxembourg with Mikey Drennan (Aston Villa) getting a hat trick. The other scorers were Thomas Hoban (Watford) and Sam Byrne (Manchester United).
Germany and Macedonia make up the group of four, and they met with Germany winning the game 5-0.
The Republic of Ireland face Macedonia tomorrow before playing their last game against Germany on Tuesday. The first of these games will be played at the same venue with the Germany game scheduled to be played at the Op Flor Stadium in Grevenmacher.