A grounded bushing would need to be used if there are concentrics where the conduit terminates. The ground wire from the bushing to the ground lug would be sized according the feeder size, just as if you were to run an EGC (equipment grounding conductor).
If there are no concentrics, you'll need to use a grounded locknut, or a connector LISTED for that purpose.
Andrew
Conductors are THHN.
Looks like there are conflicting opinions as to whether or not a bushing / EGC is necessary. Anyone have other thoughts?
As Augie stated in his post, for a voltage under 250 volts, even with concentric KO's, bonding bushings or locknuts would not be required.