Everton capture Oviedo from Copenhagen
"He can play left-back, left midfield and left wing... which will help us and give us good cover in the squad," assistant manager Steve Round told the English Premier League club's website.
"I have been abroad and watched him, as have all the scouts and the manager [David Moyes]."
The 22-year-old joined Copenhagen in 2010 from Costa Rican side Saprissa.
"I am very happy for the opportunity I now get to play in the world's biggest league," said Oviedo who has 13 international caps.
"It's really hard for me to leave because the club has meant so much to me and aided my development. I could have seen myself at Copenhagen for a long time but a switch to a historic club in the Premier League is a dream now fulfilled."