I'm adding brakes to my trailer. Should I run the brake ground to the ground wire in the plug or just have it connect to the trailer frame?

if it was me i would do both

Alrighty then. Thanks

if it was me i would do both

X2. I can't tell you how many trailers I see have problems and it's due to grounding or lack there of. If you can double it up you'll be much better off.

Make sure you use the correct gauge wire.