A popular glacier scramble above turquoise Colchuck Lake, often combined with neighboring Dragontail Peak via the col between them.
Drive to the Stuart Lake Trailhead at the end of Forest Road 7601 (Eightmile Road) south of Leavenworth. Hike the Stuart Lake Trail about 2.6 miles to a junction, then follow the Colchuck Lake Trail roughly 1.7 more miles, climbing steeply over boulders near the end, to Colchuck Lake (about 4.5 miles and 2,000 feet of gain from the trailhead). Follow the boot path around the west side of the lake, then continue toward the base of the Colchuck Glacier below the obvious col between Colchuck and Dragontail Peaks. Climb talus or snow (this slope holds snow well into summer) to the toe of the glacier, then ascend the glacier itself to the col; late in the season the glacier can be bare, hard ice that crampons don't bite well into, sometimes forcing a detour onto the rocky sidewall. From the Colchuck-Dragontail col, it is a straightforward Class 2 walk up talus to Colchuck's summit.
Descend the ascent route. If continuing to Dragontail Peak, head east from the col instead, and treat the return to Colchuck Lake and the trailhead as a separate, later descent.