Sunderland have settled on the man who they want to take over from Patrick van Aanholt in the left-back berth.
The Black Cats have had numerous irons in the fire over the past few days, with swoops for Neil Taylor and Diego Contento all considered.
Yet it is not surprise that Moyes has plumped for a man he brought into British football in 2012.
So what shape is he in and what will he bring to the table? Here's what you need to know...;
What kind of player is he and what is likely to have appealed to David Moyes?
Like van Aanholt, he can play as either a full-back or a wing-back. That will have been a big tick in David Moyes' box, who has played with a back five on a few occasions this season and feels it gives his team some much needed solidity at the back.
The Sunderland boss likely feels that the Costa Rican offers a much better balance than the Dutchman, who has completed his switch to Selhurst Park.
van Aanholt's pace and movement became a central part of Sunderland's attacking template, but the backroom staff were left exasperated by his lack of defensive positioning and at times, commitment. That came to a head with a dismal showing at the Hawthorns.
Ultimately Moyes is getting a player he feels he can trust both on and off the pitch, someone whose all energy performances made him a favourite on the Goodison terraces.
Oviedo does have an attacking threat, too, with a decent delivery. He is, however, nowhere near as quick across the ground. In the relegation scrap however, Moyes is after someone who will put the basics of defending first.
It's something he has been working on himself, saying in October last year: "Maybe I am not expected to play that differently, but I have to be more concentrated on the defensive balance.
"(The Everton coaching staff) like to be very good on the defensive balance.
"It is very important for the team. When we have possession and are on the attack, you have to be a very clever full-back because we create the balance of the team."
What shape is he in? Is he ready for an immediate impact?
Sunderland will hope so.
van Aanholt's departure leaves them without a senior left-back in the squad. Tommy Robson offers an option in the youth set-up but he has been linked with moves to Hibs and Barnsley this month.
The likes of Joleon Lescott, Javier Manquillo and Billy Jones could all fill on in that flank but that would be far from ideal.
Oviedo last played in the Premier League last November, with Chelsea running out 5-0 victors in an electrifying performance. That was a galling day for the Costa Rican but he did win plaudits for his performance in the 2-0 win over West Ham just a week previous. Overall he has played just seven games this season.
Ultimately, he has never convinced that he could be Leighton Baines' long-term successor. Ronald Koeman was keen to keep him as back-up this month but the Black Cats willingness to seal a permanent deal seems to have convinced him to sanction the departure.
In that sense he has not been helped by dreadful luck with injuries, which started when he suffered a horrific leg break against Stevenage in 2014. He has had a number of problems since then but did manage 20 appearances across all competitions last season.
He will leave Everton with 44 Premier League appearances to his name. David Moyes may well say, however, that reflects more on Leighton Baines' consistent excellence more than does on his understudy.
It is, without doubt, another gamble on Sunderland's part.
They are switching a first-team regular for someone without a history of playing week in week out. The situation was becoming so dire, however, that the time had come to roll the dice.
Oviedo himself is desperate to impress, saying just earlier this month: "This is the most difficult time I have had at Everton when I have not been injured. I’ve not even been on the bench for the past two months.
“The manager has told me it is a tricky situation, but said he needs attacking players – so I just have to wait.
“It is hard for me, as you never prepare yourself not to play. You want to be involved and taken into account.
“In the past at least I had the chance to come on as a sub under previous managers David Moyes and Roberto Martinez. Koeman calms me down a bit by telling me it is not my fault I am not playing.
“I ask the good Lord to give me patience, so I do not give up hope.
“I think about the option of joining another club, where I could play more regularly. The problem with Everton is that I’m not playing matches."
Sunderland need him to get 18 under his belt between now and the end of the season.