The Toffees have sealed the capture of the Costan Rican defender, who becomes the fourth signing of the summer for David Moyes' side
The versatile Costa Rican has been linked with a variety of clubs over the summer, but has agreed to move to Goodision Park for a fee believed to be in the region of 5 million pounds.
Oviedo can play at left back and on the left side of midfield, and his signing will give the Toffees added depth as they look to build on last season's impressive seventh-placed finish.
The 22-year-old has earned 13 international caps for Costa Rica, and has appeared in the Champions League in addition to winning a Danish league title and two Danish Cups during his time in Scandinavia.
However, despite enjoying much success in the Danish capital, Oviedo admitted that he is eager to enhance his career in the Premier League.
He told Everton's official website: "I am so very happy. This is a very good opportunity for me.
"I know a lot about Everton. I watch Everton games and Premier League games on the TV and it is a very good league.
"The last two or three days have been very stressful and tiring but I am so happy now. I am feeling good and right now everything is positive."
The capture of Oviedo could well be David Moyes' last foray into the transfer market. The Toffees have also added Kevin Mirallas, Steven Pienaar and Steven Naismith so far this summer, but have also lost Jack Rodwell and Tim Cahill to Manchester City and New York Red Bulls respectively.