The Portuguese international striker was one of ten changes made at half-time - a goal to the good following a neat finish from Milenko Acimovic.
It was Johnnie Jackson who provided the opportunity for debut joy, working space down the left before firing over a low cross that Postiga met with some force from close-range.
"It was only a step up from a practice game, but you can't ask for any better than when a lad puts on a new shirt and scores," reacted Glenn afterwards. "We're happy with that.
"He's a good player and that's why we were after him. We're happy that he's joined us, he's only young and has a lot to learn but, as you can see, there is a lot to work with.
"I think he'll score goals - he's got belief in himself and is a mature 20-year-old."
Glenn Hoddle was naturally upbeat after watching Helder Postiga score after just five minutes of his first appearance for the club at Stevenage.