There is a small parking lot in the back of Big Creek
Campground that is reserved for this trail.
Snow on the the upper section of the trail near the forest road can last through late June so the best time to run this trail is July through October.
Being on the outskirts of Mount Rainier National park Osborne Mountain trail can be easily overlooked which is a shame because it is a truly enjoyable trail. Starting from back of Big Creek
Campground follow the signs for trail number #250.
The trail starts out flat and muddy as you travel about a quarter of a mile through some swampy wetlands between the campground and the base of Osborne Mountain. From that point on it's almost two miles of switchbacks and quiet forest as you climb 2000 feet to the ridge line. From that point you can venture down the other side of the mountain along the Cave Creek
trail or continue on along the narrow but very run-able ridge towards the summit of the mountain.
After about a mile of ridge line you'll reach National Forest Road 8410. The trail itself does not summit the mountain so if you wish to do so you'll need to take a left on the forest road run about a half mile. From there you can bushwhack your way to the top for some sweeping views of Rainier and the surrounding mountains.
To reach the end of the trail continuing from the intersection of FR 8410 run down the road for about .17 miles and look for the continuation of the trail on your right. Follow the trail downhill for another mile until you reach the end at the intersection of the Teeley Creek Trail
(#251). Down that trail for another mile you'll be able to stop at both Bertha May and Granite lakes, which is well worth the extra effort.
This trail is best run as an out and back. The trail is narrow but very run-able down the ridge line. Back at the steep switchbacks you can really gain some speed as the trail is mostly free of roots and rocks. There is a small parking lot at the beginning of Teeley Creek Trail
so if you really can't run back arrange to have a car meet you there.