The Portuguese went into the group as top seeds, with Northern Ireland third seeds, and Oxtoby says the two games will be a “real challenge for us against a very good side”.
“We are a team in transition with a lot of youth coming through and these two fixtures will really test us,” said the Northern Ireland boss.
“Results are, of course, important but a good performance against a strong side like Portugal will stand us in good stead and give the team a lot of confidence. And in a high performing environment, confidence can be crucial.”
Northern Ireland squad
Goalkeepers: Burns (Reading), Harvey-Clifford (Crusaders Strikers), Perry (Montrose)
Defenders: Holloway (Birmingham City), Rebecca McKenna (Charlton Athletic), Laura Rafferty (Southampton), Demi Vance (Glentoran), Rachel Dugdale (Reading), Kelsie Burrows (Cliftonville)
Midfielders: Andrews (Glentoran), Caldwell (Glentoran), McCarron (Glentoran), Bell (Hearts – on loan from Rangers), Callaghan (Cliftonville), McPartlan (Burnley Women)
Forwards: Beattie (Glentoran), Wilson (Glentoran), Magill (Aston Villa), Wade (Reading), Halliday (Linfield), Howe (Athlone Town), Hamilton (Lewes), Maxwell (Cliftonville)