Osceola Peak is an odd name for a mountain and I had always wondered if it was named after the 19th Century Seminole Indian leader. But this would be inconsistent with the origins of the Seminole, who reside all the way across the country in Florida. Some time later (September 2003), Northwest climbing historian Harry Majors informed me that this peak was named by Lage Wernstedt after Florida's Osceola National Forest, which itself was most probably named after the Seminole Indian chief. At any rate, Osceola Peak is a high, bulky mountain that offers great views of other Washington Top 100 peaks in the Mt. Lago group. Osceola Peak is the westernmost peak of the trio that looms over the northern head of Eureka Creek. The other two peaks being Mt. Carru and Mt. Lago. As a climb from the south, Osceola Peak is a big talus bore, but more involved (though chossy) climbing can be found on the east and north sides.
The shortest approach to Osceola Peak would be from Slate Pass (on Harts Pass Road) down the Middle Fork Pasayten River to Berk Creek and then up from there to 7,100-ft Freds Pass and 6,975-ft Lake Doris (good camping). This is about 13 miles from the road. Other approaches are longer and not worth mentioning here.
Permits are not required as far as I know, though signing a trailhead register might be requested. You won't run into much civilization out in the Pasayten Wilderness. When I was out there for a week in August, I saw less than five people once I got back to the Carru vicinity. You'll see more people (and horses and dogs) on the Robinson Creek Trail, which runs along the Middle Fork Pasayten River north of Slate Pass.
When To Climb
Osceola Peak could probably be climbed in every season except winter. Access depends on conditions for getting to the trailhead. The Slate Pass trailhead is ~6,900 ft up. In fact, the road to Slate Peak Lookout is the highest well-traveled road in Washington. Harts Pass Road is also one of the more exposed roads to drive on. Combine that with the many sightseers who use the road and it becomes a concentrating endeavor. The snowier the approach, the longer time you'll need to get in and out.
There are numerous campsites. Some I know of are:
1. At a large horse camp near to where the trail to Ferguson Lake junctions off from the Robinson Creek Trail as it parallels the Middle Fork Pasayten Wilderness.
2. At the intersection of the Robinson Creek Trail and Berk Creek (this is where the trail up to Freds Lake, Freds Pass, and Lake Doris begins)
3. At Freds Lake
4. At Lake Doris
When I was in there in August 2001, I was snowed on lightly for one night at my 7,500-ft camp. Knowing this, plan your clothing appropriately. It can be hot or cold or in between in the Pasayten. Ordinarily, you won't get much rainfall as the wilderness is far east of the Cascade Crest. However, when I was there, it rained for 36 hours straight. I stayed in my tent nearly the whole time.