About 120 mounts and their riders were put through their paces and videotaped for possible selection as extras in the movie, which is to be filmed next year.
Horse co-ordinator Steve Old said about 250 horses and riders were being sought from around the South Island. Some of the scenes required more than 200 horses.
"In the book [on which the movie is based], there is a tribe of people called the Riders of Rohan. They eat, sleep and live on their horses, so we're looking for people to be able to do that," he said.
As well as looking for riding and horse obedience skills, he was picking out potential leaders who could be put in charge of a group of horse riders. Mr Old will be riding in the film.
The film-makers were seeking similar-looking horses, taller than 15.2hh, and riders with Nordic looks, long hair and possibly beards. But most of the riders on Saturday were female.
"We'll use make-up," he said.
Horses would not be exempt from make-up either, horse make-up artist Mark Kinaston-Smith said.
That meant a bit of dye here and there to match horses for different scenes, and it ruled out the use of multi-coloured horses and greys, he said.
Successful extras could end up being used for just a day, or up to several weeks, depending on the filming location, weather and scene.
Several secret locations will be used for the feature film.