There is more than one Lookout Mountain in Oregon. This one is in the Ochoco Mountains. Go east of Prineville on Highway 26 for 17 miles, and turn right on Road 42. In about 7 miles, reach a pass and turn right on Road 4205 for a rough mile to the marked trailhead. This is a 7 mile loop trail and I recommend starting clockwise on trail #808. I have hiked this trail as early as June 12th and as late as July 4th, depending on the spring thaw.
The first mile or so is in light woods and one sees mostly baneberry in bloom. The next sections transition between open meadows and a diversity of trees. There is a lot of false hellebore (cornflower) in the meadows, as well as currants, stickseed, bluebells, valerian, and checkermallow. A little further up the trail, Brown’s Peony begins to appear–a specially odd and beautiful flower not to be missed. Two tiny lewisia’s begin to appear (relatives of the larger, showier Bitterroot). I’m guessing they are nevadensis and triphylla. And all along the trail there has been a lot of ball-headed waterleaf, fleabane, balsamroot, desert parsley and arnica, so many plants, in fact, that my list (available upon request) nearly fills two pages.
When the summit is reached, one finds the strange little speckled-pod astragulus, yellow paintbrush, and columbine growing amid the sagebrush. This is fine place for lunch as the view west to the Cascade peaks is unbeatable. To complete the loop, be sure to stay on trail #808 at the old lookout site and past the log shelter. At the shelter, there is a fine view to the east toward Big Summit Prairie.
In a short while, a junction of trails #808 and #808A is reached. The most direct route back to the trailhead is #808A. Trail #808 on the left takes a longer route past the old Mother Lode Mine site.