He first alighted in Dingwall a year ago to join a team on its way into the top six of the Scottish top flight last season and his performance on Saturday would suggest that he has still to take account of the club's new circumstances. County are in the SPFL Premiership's relegation play-off place, with the club securing only their fifth league win of the campaign on Saturday.
Similarly, Oikonomou would take time to settle - he has returned to Scotland after an ill-fated summer move to Greek Super League side Veria - but found his feet in time to provide an assured performance on the left side of the County defence. That would delight home supporters at the weekend and also reaffirmed Brian McLean as a fan of the Greek - with the County defender extolling his team-mate afterwards.
Oikonomou's display was emblematic of the confidence which has been recaptured by Derek Adams' team as they seek to revive their season. Much like last year, he comprises one of a plethora of new signings, with on-loan Rotherham United midfielder Michael Tidser making his debut at the weekend and Jordan Slew - who has arrived on loan from Blackburn Rovers - starting for the second time up front for the Highland side.
Adams has promised that there will be more signings this month and Filip Kiss, Cardiff City's Slovakian under 21 internationalist, watched from the main stand in Dingwall, with his loan deal set to be completed early this week. He would likely have enjoyed the sight of Graham Carey scoring a decisive late goal, although McLean was moved more by the display of Oikonomou.
"Evangelos has only just come into the team so, for the first five or 10 minutes he was looking for his second wind," said the County defender. "He found it. It's not easy coming in like that, especially having been out of favour at his previous club. He is very composed, to say the least. There were times I expected him to hack it clear and he would take a touch and make a pass.
"He is the sort who will keep the ball for us and he did exceptionally well. Ben Gordon, moving across to right-back from the left, didn't look out of place either. Collectively, we held it together very well and the team as a whole looked solid. We got the result we deserved."
The Dingwall side have taken flak for repeated defensive lapses this season and there was certain pride evident as McLean appraised the solidity shown against St Johnstone. His partnership with Scott Boyd appears to be blossoming, too, but the 28-year-old would also credit the frontmen for the improving display.
"I think everything has just clicked into place and it has been a great start to the year," said McLean, whose side kicked off 2014 with a derby win over Inverness Caledonian Thistle. "Jordan Slew, coming in up front, has been superb alongside Gary Glen. The two of them together have been a revelation for us in the last two victories. As a defender, it eases the pressure on the back four and allows us to get up the park and keep a stronger grip on the game.
"We've deserved to win the past couple of games. It is amazing the difference a win makes to the mood and confidence about the place. It hasn't even been a week, so it has been brilliant for the dressing room. It has fed into everybody and it's pretty infectious in there. Long may it continue."
St Johnstone could perhaps do with a similar injection of optimism after a downturn in results during the festive period. Defeat on Saturday has contributed to an uncomfortable series of results which contains just one win in six matches. Tommy Wright felt his side lost by fine margins against County, although he was concerned by such faltering form from his players.
"It was always going to take a wonder goal or a mistake to win it - and that proved to be the case," said the St Johnstone manager, whose side will see out the season without Gwoin Edwards after the Swansea City winger chose to end his loan spell early.
"Although the pitch looked magnificent it was quite slippy. We should have come away with at least a point. We had a lot of good opportunities but the final ball was poor and both defences did well.
"The festive period should have been better with three defeats and a win. We are in a run at the moment, particularly away from home, where we are getting punished for every mistake."