James Hanson's goal shortly before half-time was enough to for Parkinson's in-form side to triumph 1-0.
Bradford reached the League Cup final only to crash 5-0 against Swansea of the Premier League and their hopes of a play-off place looked slight indeed after losing 4-1 at rivals Exeter five weeks ago, but they have earned 17 points in the eight matches since then to make sure of finishing in the top seven.
"It has been a fantastic turnaround since Exeter," said Parkinson. "We were five games unbeaten (after the Wembley defeat) going into the Exeter match, but after we lost that game we had the players in on the Sunday to watch the video and told them what we had got to do to get where we wanted to be.
"We have turned it round through sheer hard work, desire and professionalism and it is not just the 11 players on the field who have got us into this position - it has been a squad achievement.
"The lads have been terrific, it is what this club deserves and now we have got the chance to go Wembley (for the play-off final) twice in one season and when the play-offs start I think the support we will get will be unbelievable for a club at this level.
"The support we had was brilliant and the lads have enjoyed playing in front of our supporters.
"I am pleased our play-off place has been decided. I didn't expect it. You always have it in the back of your mind that it is going to the last game of the season. Now it gives me a chance to rest players who are carrying injuries like James Meredith and Garry Thompson.
"We are going to be involved with some big games and we are going to give them our best possible effort. Mentally and physically we are prepared for them."