A quick search turned up a short list of feed additive medications, not all of these are used in quail feed typically but I thought I would include them all. Avatec(Lasalocid), BMD(Bacitracin Methylene Disalicylate), Bio-Cox(Salinomycin), Coban(Monensin), Corid(Amprolium), CTC(Chlortetracycline), Rofenaid(Sulfadimethoxine and Ormetoprim). You may also see copper added(though I don't recall which species of livestock it is and is not okay to give copper supplements to), while not a medication per se it is therapeutic in that certain parasites are killed by contact with copper.
A medicated feed will have the name of the medication, the percentage or amount to volume, and usually what it treats. If you see any registered brand name looking that up should yield a medication product sheet, or if you see any of the generic names above. Anything outside of that list you can try to look up if it looks out of place on your ingredient list.
Personally I am in favor of keeping hygienic conditions, quarantining incoming animals, and only treating animals if or when needed. Chronically medicating well animals means that any ailment able to survive and effect them will be resistant to the medication, reducing your options for treating it and breeding stronger, more medication resistant, diseases.
As said before, it all breaks down to personal preference in husbandry practices.
Cheers,
Jessie