The star-studded Welsh region put the Italian minnows to the sword with four tries in either half at the Stadio Giglio.
Now the Ospreys have put themselves in pole position ahead of the return fixture at the Liberty Stadium next Saturday.
Assistant coach Humphreys said: “We’re delighted with the outcome because we know that Viadana is a difficult place to play.
“We were tactically precise and apart from the first 20 minutes we played some good stuff. There was a good balance to our game which allowed us to attack with purpose.
“We have given ourselves a platform to push on from in this group and we’re really focused for the return clash next week.”
The Ospreys, without several first-team regulars such as Ryan Jones, Shane Williams and Lee Byrne roared to the summit of the ‘Pool of Death’ ahead of rivals Leicester Tigers and Clermont Auvergne who clash in France today (Sun).
The Welsh region gained maximum points inside 33 minutes following strikes from Alun Wyn Jones, Nikki Walker, new signing Ricky Januarie and Jerry Collins.
Fly-half Dan Biggar scored a perfect ten kicks in a 22-point tally while hooker Richard Hibbard grabbed a double with backs Tommy Bowe and Gareth Owen also crossing.
Viadana fought to the end and claimed a consolation try through Welshman and number eight Gavin Quinnell.
Stand-in skipper Collins said: “We played some good stuff and made a few breaks in midfield. The difference was we were able to finish them off. In previous weeks we have had chances but not converted them.
“Of course, we have had problems with injuries but we hope that is now behind us.”
