The Peter Lock-trained galloper strode away to win by more than three lengths in open company over 1600m.
The win was Johnson’s 101st for the season.
His victory aboard Tuilana in the last race at Ashburton on Tuesday brought up win 100.
It is the second consecutive year Johnson has cracked the 100-win mark. Johnson made an admirable fist of defending his National Jockey’s Premiership crown from last year. He sits in second behind runaway leader Samantha Collett, who added a double on the day to move to 121 wins with just over three weeks of the season left to run. Lock admitted he had some concerns about Johnson’s strike rate for his stable before the race.
"When I looked up the stats it wasn’t the track I was worried about," he said.
"I think he’s had six unplaced rides for me, so I was more worried about that."
Johnson settled a keen Dougie three-wide with cover early before the horse pulled his way to being outside the leader.
Dougie travelled comfortably on the turn and had plenty in reserve in the home straight.
"He’s a horse on the move who has just got better and better this time in," Lock said.
"He travelled into it really nicely today and at the half mile he was always going to win the race.
"He was a very weak and immature horse early on but he always showed he just needed time.
"We work him on the treadmill we have at home now and that has really settled him down."
Dougie is likely to be set for an Australian campaign and accompany stablemates Mr Luigi and Hiflyer.
"I’m pretty sure we will be heading to Australia with him now," Lock said.
"There’s a benchmark 1600m race for $100,000 in a fortnight so that will be his first target.
"Mr Luigi will also run for $100,000 in his grade at Rosehill this Saturday, while Hiflyer will tackle a listed 1400m handicap race there as well.
"Johnathan [Parkes] is coming over to ride Hiflyer and if he does everything well then, we will look at something bigger and better later on.
"Our main aim is to go there to look at that and see how we go."
— Additional reporting NZ Racing Desk
