Start at the Avalanche Gulch Trailhead and follow the Colorado Trail to Mount Yale via the Mount Yale East Ridge Route.
From Mount Yale, return east along the ridge for a couple hundred yards. Use your best judgement to decide exactly where to begin your descent on Yale's south side. This is a somewhat nasty slope of scree. USE CAUTION in your descent, and take your time in getting down to the obvious saddle between Mount Yale and Mascot Peak.
From the saddle the ridge up to Mascot is a fun talus scramble all the way to the summit. The views of Mount Yale and Mount Princeton are awesome! Also, stay on the ridge-line or to the west side of the ridge. There are surprising dropoffs on the ridge's east face, with some startling views down into Avalanche Gulch.
The hard part about Mascot Peak is deciding how to get down. DO NOT DESCEND via Denny Gulch to the west. Instead, you will either have to re-ascend the east ridge of Mount Yale, or drop down into Avalanche Gulch and bushwhack your way down the gulch to the Colorado Trail. Although Gerry Roach described the latter as one of your options for descent, I did so and noticed a couple things you should be aware of:
1. The descent from the 13,060-foot Yale-Mascot saddle is every bit as slippery and dangerous a scree slope as the slope descended from the saddle up to Mount Yale. USE CAUTION! Take your time!
2. There is no hiker's trail that I was able to find in Avalanche Gulch. The terrain is rough at places and there are logs down everywhere (hence "Avalanche" Gulch). Thus, be sure you know where you are and where you are heading at all times. I had a GPS to assist me, and mostly stuck to the northern edge of the gulch, at the base of Yale's east ridge, following game trails.
Once back out to the Colorado Trail, follow it back out the rest of the way to the Avalanche Gulch Trailhead.
For summer hikes, nothing special. Shoes with good traction, GPS highly recommended.
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