The road to Glass Butte requires a high clearance vehicle and four-wheel drive is recommended. This road is at the limit of what a rear-wheel drive, open differential vehicle can travel. Although it may not be the most scenic summit, if you are traveling through eastern Oregon this is a worthy six-point peak to check out, especially in conjunction with an activation of nearby Little Glass Butte.

The PDF map below was helpful as there are currently no signs indicating turnoffs to Glass Butte from Highway 20. From Bend, the best access is the dirt road heading south just before MP 77. At about 2.9 miles there is a pond and the main track APPEARS to head east at this point. However, the road heading south to Glass Butte is a RIGHT turn just past the pond (this is different than what is indicated on the map). 

After about 2.5 miles turn right up an unmarked side road. The next five miles is very rough. Stay on the main track - it winds back and forth but eventually the summit will come into view. The final bit of road is quite steep and rough - I choose to park at a wide spot and walk about 0.4 miles up the road for the final ascent. I noticed no particular RF noise from the radio installations here but kept my distance within the activation zone just below the summit proper. There are a few trees that could be used to support the end of an antenna.

Although there are bits of obsidian all over the roads, as a side trip you could check out one glass "mine" just off the main road at this location: 43.55520 -120.00696. There are probably dozens of such pits, but this one is easy to get to. There's a campsite just off the main road where there is a short trail up the hill. Have a care handling any glass as it is quite sharp - gloves are a good idea.  

Note that although there are good signals for T-Mobile voice calls, SMS messages did not go through from this Unicel roaming area.