Are you buying direct from the mill or from a warehouse? Hot rolled, or turned & polished? You can write a material purchase specification to list your bar quality level, straightness requirements (ex. .25" in 60"), tensiles. If you're concerned about rolling defects the bars can be inspected prior to reaching your shop for seams, laps, objectionable nonmetallics, etc.
You can have many aspects of the bar inspected, depending upon the safety and functional requirements of the end product. More requirements may mean more raw material cost. You may want to consult with a materials engineer to help write a purchase spec. Even then if it is a safety part you may need to verify a few things. Hopefully this is a start.