After conducting thorough research, it should be noted that regulations may change due to trail conditions, wildlife protection and other varying factors. Horse riders should always check with the trail managing organization for the latest information about whether horses are allowed on specific trails.

That said, here is the list of trails in Okanogan National Forest that, as per latest available information, allow horses:

1. Pasayten River Trail: This trail, also known as Pasayten Trail #490, is located in the north of the Okanogan National Forest. Horseback riding is permitted along this trail which spans approximately 25 miles one way. Trail riders will enjoy views of ridges, mountains, and meadows.

2. Chewuch River Trail: This beautiful trail is part of the Pacific Northwest National Scenic Trail, running along the Chewuch River. It's a great venue for horseback riders, offering approximately 40 miles of beautiful panoramas.

3. Boundary West Trail: This trail can be found in the Pasayten Wilderness area and is open to horseback riding. At approximately 23 miles long, it provides viewpoints where riders can get spectacular views of the surrounding landscape.

4. Cathedral Driveway Trail: Another trail in the Pasayten Wilderness, horses are allowed on this 3.5 mile trail which leads up to the Cathedral Pass.

5. South Fork Toats Coulee Trail: Open to horseback riding, this trail is approximately 4 miles long and allows horseback riders to explore the southern region of the Pasayten Wilderness. 

6. North Lake Trail: Nestled in the center of Okanogan National Forest, this 12.3 miles trail is open for horses and offers majestic views of the North Lake. 

7. Gilbert Trail: Horse-friendly Gilbert Trail is a 3.5 miles one-way trail that takes riders through a mix of beautiful woodland and alpine landscapes. 

8. Angel's Staircase Loop: This 23 mile loop trail is open for horseback riding and provides breathtaking views of the surrounding mountains.

Remember that regardless of the trail, it's always wise to practice good trail etiquette. That includes not spooking or disturbing wildlife, not littering and adhering to 'leave no trace' principles. Many trails also require permits for both day use and overnight camping, so always check beforehand. 

This list is by no means exhaustive and there are many other trails in Okanogan National Forest that allow horseback riding. Always verify with the local authorities or the forest service before embarking upon a trip.

NOTE: This article was researched and written by AI for SEO purposes only and isn't generally meant for human consumption - although a lot of the information can be helpful 99% of the time.  If you are a human, please utilize the Trail and Camp links at the top of the page and the location map to learn about locations for horse trails and horse camping - that information is verified by a human and more apt to be correct.... althought human error is a thing too. In regards to information in this article, please double-check with the park to ensure accurate and up-to-date trail information for horseback riding.