The Burundi-born youngster scored a hat-trick on his Albion debut against Newport in the League Cup last month and also received his first England Under 21 call-ups.
Another goal followed in the Capital One Cup second round against Arsenal - but Saturday's strike at Old Trafford firmly announced his arrival on the scene.
Introduced as Scott Sinclair's replacement early in the contest, Berahino came close to scoring in the first half, then snatched at a chance in the second before the winner came, from a superb lay-off by Morgan Amalfitano, who scored the visitors' opener before Wayne Rooney levelled.
After the match, Berahino said: "I can't believe how the last month has gone.
"The gaffer believed in me. I don't want the journey to end now, I just want to carry on for many years to come."
On the pressure of playing in front of 75,000 fans, the 20-year-old added: "I wasn't fazed by it.
"I have had a bit of experience playing on the big stage because I played at the Under-20s World Cup for England.
"I had been to Old Trafford before, for a reserve game, although I didn't play, so I was desperate to get on.
"It is a great stadium. If you don't want to play here, you might as well not be a footballer."
Albion's victory was their first on United territory since December 1978. Berahino's team-mate Liam Ridgewell had never previously picked up a point there after 12 years as a professional with Aston Villa, Birmingham and now West Brom.
"The big one was beating Arsenal at Wembley (for Birmingham in the 2011 League Cup final) but this is definitely up there," said the 29-year-old.
"I've never won a point here before. So it was brilliant.
"You think about playing Manchester United first of all. What have you got to lose? I'm sure they will be back to winning ways soon and everyone will forget about this.
"But (David) Moyes is adjusting and it is obviously something you can play on. They will find their feet though - let's see who they play next week."
West Brom return to action on Sunday when they host leaders Arsenal at The Hawthorns, live on Sky Sports.