England midfielder Oxlade-Chamberlain was forced off in the 5-0 FA Cup quarter-final win over Lincoln last weekend with a hamstring problem but it was more of a precaution and he could be involved at The Hawthorns.
Welbeck and Alex Iwobi have overcome illness but Kieran Gibbs is a doubt with an unspecified knock, while Mohamed Elneny (ankle) will miss out again, despite returning to first-team training this week.
Santi Cazorla is a long-term absentee due to an Achilles injury.
Boss Arsene Wenger admits Arsenal face a tough task getting into the top four having slipped five points behind Liverpool and the Frenchman says three points is a must at West BRom on Saturday to keep pace with their rivals.
"We want to play in the Champions League next season," said Wenger. "We have a tough job because we have six or seven teams fighting for the places and how well we do until the end of the season will of course depend on that."
Provisional squad: Cech, Ospina, Martinez, Bellerin, Holding, Gabriel, Mertesacker, Koscielny, Mustafi, Monreal, Gibbs, Maitland-Niles, Coquelin, Xhaka, Ramsey, Oxlade-Chamberlain, Ozil, Walcott, Reine-Adelaide, Iwobi, Perez, Sanchez, Giroud, Welbeck.