The West Bromwich Albion striker, who was top scorer in the qualifying stages for this month’s European Championship Finals, also enjoyed a productive campaign in the Premier League.
His goals early in the season brought him recognition from Roy Hodgson and he was called into the senior squad for the first time last November.
Berahino in action in the 1-0 win over Belarus on Thursday
But he is now with Southgate’s squad after a strong end to the term and is heading to Czech Republic aiming to finish what he started - his first U21 strike proved the winner against Moldova back in September 2013.
"I think it’s been an interesting season for him, first of all in terms of establishing himself in West Brom’s team and getting himself as first choice," said Southgate.
"He is another who is a quality finisher. If you put sessions on, the quality of his shooting is very good.
"I think he will have been overlooked by other countries with Harry being in the squad. But I don’t think that is a bad thing because he can have a real impact."
Saido's GoPro shootout
Head coach Southgate also believes working under Throstles boss Tony Pulis, following his mid-season appointment at the Hawthorns, will have brought another dimension to Berahino’s game.
It certainly reflected in his goalscoring, with a flurry of strikes in April and May taking his overall tally to 20 to put him in good form ahead of the Euros.
"Working with Tony would have added other bits to his game, in terms of tactical understanding," revealed Southgate.
"That helps from our point of view, because there are demands we ask of our players when they haven’t got the ball. Tony will work on that a lot in a certain way.
"Saido responded to that and Tony was delighted with him, towards the end of the season in particularly."
One thing which Southgate has previously alluded to and continues to be impressed by is Berahino’s commitment and determination to improve.
Saido celebrates scoring for the Young Lions
Southgate cites an example of that last summer, when he returned from the Toulon Tournament in France unhappy with his condition. So Berahino went to work with his own fitness coach for the close season.
"He has been a pleasure to work with," added the former Aston Villa defender.
"It’s clear there have been a couple of dips off the field in the last year. But what I like about him is that there is always recognition - there is never a denial.
"This year he got himself physically right in pre-season, he got himself in great shape.
"The reward was getting in West Brom’s first team. You hope as time goes on, there are fewer dips and then none at all.
"He has got a fantastic chance of being a top player."
