From the abrupt end of FR579 walk NW on a trail that takes off from the end of the road and continue on a NW contour on that trail into the trees until it intersects the Colorado Trail after about .2 mile and shortly before the Colorado Trail drops down to cross an unnamed fork of Cascade Creek. On some maps, this trail use to be called the Rico-Silverton Trail. Once you find a way to cross the creek (may be more of a problem earlier in the season) follow it east to these coordinates: N 37° 43' 47.19" W 107° 51' 41.32". Here, another, less used trail heads off contouring east uphill above the Colorado Trail. Follow this trail through open terrain for a while as it heads more steeply uphill, then turns north onto a bench area at just about tree line. The trail crosses a brief scree field, goes a short distance, then comes to the tongue of a large rock glacier. It crosses through it at about these coordinates: N 37° 44' 09.63 W 107° 51' 19.53". The trail continues on the timberline bench to yet another rockslide area. If you attempt to skirt at the bottom, you will find willows. If you don't like that choice, walk across the bottom end of the rock glacier. Choose your poison. Once on the other side, the trail will continue to an unnamed pond/lake at 11,560 ft. Backpackers will find some nice camping here.
Now the fun begins. From the unnamed lake, to the west will be yet another rock glacier that you'll want to avoid. Looking at the summit of Grizzly, you will see a large cleft-like couloir almost directly below what appears to be the summit. Follow the west (left) skyline ridge down past a rocky buttress to yet another prominent couloir. That is your basic destination. Ascend by the best route you can find in a NW direction to a small basin at 12,140 ft. On the map we supply, this is about where the ascent and descent routes intersect. Hike in the direction of the couloir mainly on grassy slopes with rock outcrops interspersed. Enter the couloir at about 13,100 ft. Earlier in the season, the couloir will still be filled with snow and a minimum of an ice axe will be welcome. If there is no snow, then it is all loose rubble. We climbed this summit on July 29, 1995 and found the couloir filled with snow. 1995 was a particularly heavy snow year in the mountains.
Slug your way up the couloir and top out to find a moderately tilted, wide open slope of mostly small scree/rock and patches of snow earlier season. Follow the south ridge toward a false summit then head left over to the high point following the ridge line for a little bit of scrambling at the end where there is a little false summit that requires scrambling down some and then re-ascending to the true summit. The summit is mostly comprised of large blocks of rock. The north face of the peak drops off precipitously. The ridge that connects to V.10 holds nothing enticing. There's an outstanding view of the large basin at the head of Cascade Creek. From here, you could enjoy views of the Needle Mountains, Grenadiers, La Platas and Dunton Meadows.
For the descent head back as you came or try the following: Walk back down the Class 2 south ridge that you came up and continue past the head of the access couloir. Continue along the ridge on large blocks of rock with tundra ledges in between. The ridge leads to a small, pinnacle-like summit which you may want to climb for the pure fun of it. Contour around the pinnacle on its east side and then begin to drop down to a broad, grassy slope which will lead directly south and will eventually connect back to the ascent route. Just stay away from and off the rock glacier. We completed this climb with our kids, ages 12 & 14 at the time in a little over six hours.
Links to other information, routes & trip reports for this peak that may be helpful.