ApproachStart by climbing the Horsetail Falls route to the top of the falls. If the scrambling there bothers you, don't go further. Once you reach the top of the falls bear left and after about a 1/2 mile of scrambling up and down small ridges head upward toward the obvious couloir on the east Face.
Route DescriptionOnce you're near the base of the couloir, look for the obvious route. In late spring/early summer there will be a big stream/waterfall. The stream is marked on the topo map. Stay to the climber's left of this in the couloir. There is much more difficult climbing around this route. Taking the obvious path of least resistance generally leads to the right path. LOOK BACKWARDS, routefinding on the descent is the crux of this route. The couloir tops out roughly at the south corner of the pyramid just above the trees and a small lake. Once you're on the ridge it's just easy boulder hopping to the top. Don't be tempted to turn onto the north ramp on the descent, unless you're happy with exposed 3rd class downclimbing. Make sure you register where you topped out on the couloir and can find it for the descent. While not technically very difficult, there is a lot of elevation gain on this route, keep something in the tank for the way down.
Since there is a topo posted on this page that incorrectly describes this route and leads to a much more sketchy terrain, I have posted the route in Google Maps.
East Face Couloir Route
View East Face Pyramid Peak in a larger map
Essential GearIf there is sufficent snow, crampons and either ski poles or ice axe would be very handy.
A short length of 7mm rope would be very handy if you got lost on the descent.