Onion Mountain is a relatively easy trip for the traveler to Southern Oregon who wants to do a little SOTA while visiting. It's close to Grants Pass, has a fairly good road, and only requires a mile or so of hiking. To boot, it offers great views.
From the Grants Pass area, take Highway 199 towards Selma and Cave Junction. Just past the bridge over the Applegate River turn right on Rivebanks Road . Follow Riverbanks for a couple of miles until you can follow the "Onion Mountain Lookout" sign off Riverbank Road, near Griffin Park. The road is 10 mi, and is mostly gravel, but well maintained. About 7 miles along on the road, you come to a T-intersection with no sign. Backtrack a hundred yards or so and park safely, then proceed up the road on foot. Shortly after passing the gate, you'll be able to see the lookout building to your left. The walk along the road to the top takes 30-45 minutes.
The site has several communications sites, which could be a problem on VHF, though I didn't notice trouble. The lookout itself is still serviceable, and it's easy to climb it and to operate from the walkway around it. There are several trees, which I used to suppot wire antennas.
As always, bring water and check the navigation before and while going.