The second oldest show that still exists. Only about 90 minutes worth, decent sound quality, mostly music. 

Playlist

Pungeant Stench "Happy Re-Birthday"
Suffocation "Mass Obliteration"

EvilDead "The Underworld"
Drop Hammer "Pull the Rug Out"
Meshuggah "Cadaverous Mastication"
Metallica "Killing Time"
Armed Forces "Hard as Nails"
The Mighty Mighty Boss Tones "Sweet Emotion"

Sodom "Sodomy and Lust / Stalinorgel"
Exodus "Verbal Razors"
King Diamond "Halloween"
Venom "In League with Satan"
D.A.M. "My Twisted Mind"

C.O.C. "Damned for All Time"
Holy Moses "Two Sides Terror"
Death "Suicide Machine"
Gorguts "Innoculated Life"
Immolation "Those Left Behind"

Carcass "Corporal Jigsore Quandary"

As far as we know, this is the oldest show still in existence from The Metallic Onslaught. This dates to July 1, 1989, and was one of the first, if not the first, show that Joe hosted. Joe was hosting a show in Auburn, NY prior to this, but this may have been his first time on The Metallic Onslaught. This is not the whole show, but it is all we have.

Listen

So this is only a few minutes long. A snippet in time. The Metallic Overkill was the show Joe Wyatt hosted in Auburn, NY on WDWN prior to taking over The Metallic Onslaught. This may very well be the only recording in existence of it. The sound quality is poor, but as a piece of history, it is what it is.