A late Gonzalo Camacho try and Nick Evans conversion sealed a remarkable win after Stade had opened up a six-point lead as Quins failed to find their feet in the second period.
Easter and co had arrived in the Welsh capital on the back of an historic semi-final triumph over European giants Munster at Thomond Park but the England No8 admits that Friday night's performance didn't hit the heights of that heady afternoon in Limerick.
But while the quality of their efforts might not have been as perfect as they would have liked, Easter knows the character on display was second to none.
"It's credit to the guys' never-say-die attitude," said Easter, after Quins made it eight wins from nine Amlin fixtures this term.
"It would have been very easy to get our heads down when they were playing very controlled pick and go, drop goal sort of rugby, but we never gave in.
"Second half, we didn't really play at all. We were very poor and they controlled the game. But it's testament to the way we play because you've got to defend for the full 40 and the full 80 against us.
"When we actually decided to hang on to the ball rather than try silly offloads and put pressure on ourselves, we caused them problems and we took our only chance in the second half.
"I think Munster was a breakthrough game, probably the biggest since we last played Stade in the Heineken Cup. Away wins are the ones you treasure, as well as finals, and it did give us belief.
"We were nowhere near as good as we were against Munster but we still dug in and that's the kind of team spirit we've got here."
Victory on Friday night saw Quins accomplish two significant feats.
The first was to end a seven-year trophy drought, while the second was to qualify for next season's Heineken Cup.
Unsurprisingly, both achievements mean a great deal to a man who has now played 150 first-team games for the London club.
"It's massive," added Easter, who joined Quins the summer after their 2004 Amlin Challenge Cup win over Clermont Auvergne.
"I've been here a long time and we haven't won any tangible silverware.
"This competition has been great this year but with the group of guys we've got and how we want to move forward as a club, playing in the Heineken Cup is where the boys want to be. We want to be playing against the best regularly."