Environment spokesman Duncan MacDonnell says the five-year agreement with the Wild Horses of Alberta Society came into effect Nov. 1.
It calls for the society to oversee a contraceptive vaccine program for mares to try to lower the wild herd population around Sundre.
It also allows the society to adopt out horses and foals that have been captured, abandoned or injured.
The projects are being funded entirely by the wild horses group, which must be able to document the results.
MacDonnell says the province will still be involved in controlling much of the population.
"We haven't handed off all management responsibility for feral horses," MacDonnell said Tuesday.
"We are considering other management activities on the remainder of that equine zone and the remaining five zones of the designated horse capture area."
A roundup earlier this year upset animal rights activists, but others said the horses compete for grass with cattle and wild animals such as elk.
MacDonnell said the government is considering all its options and should have a better idea of its plan for next year by the middle of December.
Last March, Alberta Environment said it counted 880 feral horses in the Rocky Mountain foothills.