Although it is not within Zion National Park, Lambs Knoll is literally right across the road from the park boundary and is for all intents and purposes but legal ones a Zion peak.
A nice objective for a two- or three-hour outing, Lambs Knoll has a few distinct summits. Reaching the highest of them requires Class 3 scrambling on the approach and some borderline Class 4 moves on the summit block.
From the summit, there are sweeping views in every direction, but the best are those to the east, where the signature peaks of the remote Kolob Terrace area (most notably North Guardian Angel and South Guardian Angel) and the west rim of Zion Canyon (most notably West Temple and Mount Kinesava) are on display.
Lambs Knoll is not for climbers only. It boasts some small slot canyons, some with long pouroffs, and bolts and slings I found in some locations attest to the fact that it is not unknown to canyoneers.
When To Climb
Spring and summer are best. The road is usually open this far in winter, though. Summer temperatures can be very hot; although it's a short outing, have plenty of water and start very early or late in the day.
Getting There and RoutesFrom Virgin, turn north onto Kolob Terrace Road. This road, even though it passes through Zion National Park, is not signed for the park, but it is signed for Kolob Reservoir. Drive 9.5-10.5 miles on this paved road until you pass Tabernacle Dome on your right. Shortly after that and passing a private residence on the left, you are going to use one of two parking options. The first is by a gravel pit on the left. The second is not far past it. Details for them are included in the route descriptions.
From the Gravel Pit
I'm including this route because it is described in a guidebook that was pulled from stores (by the author) in 2010 but which I know other SPers own. This route was my ascent route, and it wasn't hard, but I do not recommend it since I "discovered" a much better way on the descent.
Skirt the fenceline around the gravel pit and head for the northeastern face of the peak. Visible the entire way is an inset, brushy area with gullies leading almost all the way up the peak. Your goal is to get to those gullies and climb up them. The catch is that the approach is very brushy and not the slightest bit fun even though it is short. And lower down, the gullies are no bargain, either.
Once you exit the top of the gully system, you are at a saddle of sorts. Going left (east) takes you to a Class 3 scramble up an exposed false summit. It's worth doing, though, because this false summit might provide the best Zion views to be had anywhere on the peak, for nothing obstructs the scene to the east.
To get to the real summit, though, head west along a ledge system (very exposed in places) and reach another saddle. Scramble up and then scramble a little more (Class 3) to reach the second-highest summit on the peak. From there, the true summit is visible, and it is less than a quarter-mile to the west. Descend and hike across a sandy, slightly brushy basin and then access the summit block via a gully. There are some different options for getting atop the summit block, and they range from Class 3 to Class 4.
Distance is 1-1.5 mi. Elevation gain is about 500'.
The Better Way
Less than 0.5 mi north of the gravel pit, spot a dirt road on the left. It is immediately after a cattle guard that marks the Zion boundary. Turn onto this road and drive less than a fifth of a mile to its end. There, you should see a sandy trail heading off towards Lambs Knoll. This road is bumpy but probably negotiable for most passenger cars when dry. When wet, it will be a quagmire.
Follow the trail to a dry streambed, and then turn right (upstream) and follow the streambed until you reach the peak's walls and short slot canyons. Follow your nose or do some trial-and-error to find the right canyon that leads up to the sandy basin mentioned in the previous route description. The difficulty should not exceed Class 3. Then head for the summit per the directions above.
I did not GPS this route, but it took me just 25 minutes to descend from the summit to the dirt road. That included some dead-end route attempts when I ran into pouroffs where there were bolts and slings (I did not have my rope), so the distance this way is probably less than a mile.