There's just this: https://www.greyhoun...nformation.aspx.
Overweight carried the same costs as oversize, but they generally won't care if the bag is less than 60 lbs unless the bus is packed with freight and isn't a G4500.
Actual luggage capacity depends on the bus model. On any Prevost, the bin height is 9", on MCI D-units, the bin height is 10", on MCI G4500, there should be more but I'm not sure. G4500s have ridiculous luggage capacity and haul lots of freight on routes heavy with Package Express.
Anyways, whatever you do, take evasive action against Greyhound's new torture machines and avoid riding routes that pretty much only use them. You'll be glad you did!
Avoid Los Angeles-San Francisco, -Sacramento, -Las Vegas, -Dallas, -El Paso, -Denver. Avoid Denver-Las Vegas/Reno/Portland. Avoid San Francisco-Sacramento-Reno. Avoid routes in the Northeast; ride Peter Pan or Trailways instead. Avoid Florida and Georgia intrastate routes.
You can get around a lot of the torture machines by taking through schedules. Long through schedules from far-away places usually have more freight, which means Blue G4500s, which means torture-machine evasion, more legroom, and more luggage capacity. New York-Los Angeles, longest route in the system, is a Blue G4500 every day.
I really do love and hate Greyhound at the same time, don't I?