Williams tormented Calvisano all game
Calvisano: (13) 27
Tries: Cittadini, Zanni, De Marigny
Cons: Scanavacca, De Marigny (2)
Pens: Scanavacca (2)
Ospreys: (33) 50
Tries: Marshall (2), S Williams (2), Bennett, Hook, Parker, Byrne
Cons: Hook (5)
The Ospreys gave a clinical performance to ease to an eight-try, bonus-point win at the Centro Sportivo San Michele.
A first-half blitz from Justin Marshall, Shane Williams, Huw Bennett, James Hook and Sonny Parker saw the bonus point secured inside 30 minutes.
With Ian Evans outstanding in a dominant pack, Williams and Marshall completed try braces after the break, Lee Byrne rounding off Ospreys' tries.
Lorenzo Cittadini, Alessandro Zanni and Roland De Marigny got consolations.
I was pleased with a number of individual performances, particularly the two young second-rows
The Ospreys will be looking for a repeat performance in the return game at the Liberty Stadium next Friday to maintain the pressure on Stade Francais and Sale in their group.
Ryan Jones (flu) was a late withdrawal in Brescia, but it did not break the visitors' stride.
After just two minutes a Marshall grubber kick was taken on by Byrne and Alun Wyn Jones, the Wales lock finding Marshall for the opening try.
The Welsh side turned over a Calvisano defensive scrum and Parker quickly fed Williams, who skinned opposite number Michael Gallinetti for a superb score.
We must be honest and accept that we don't have the quality to compete at this level
Calvisano coach Marc Delpoux
Calvisano hit back with two Andrea Scanavacca penalties, but the Ospreys were spurning kicks at goal and soon got their reward.
A short-range line-out was taken by Wyn Jones and a well-worked forward drive was rewarded with Bennett's try.
Marshall directed a series of mini-rucks before delivering the ball to outside-half Gavin Henson, whose grubber kick was gathered by inside centre Hook for the bonus-point score on 30 minutes.
Marshall crossed for an excellent brace of tries
Williams' quickly taken tap penalty was rewarded with Parker's score, but the Italians hit back on the stroke of half-time as tight-head prop Cittadini ploughed over for a try.
The visitors were straight back into their stride after the break, Williams setting up the forwards with a strong run before getting the ball back and dancing over for his second score.
Not to be outdone, Marshall got his brace after a long attack involving Williams, Duncan Jones, Hook and Byrne.
The scrum-half was then replaced by Jason Spice who sparked a break-out, and when the ball came back to Evans the Wales lock put in an unlikely grubber kick for Byrne to cross.
Calvisano bravely refused to throw in the towel and were rewarded when their star performer - number eight Zanni - crossed for a deserved try after good build-up work from Gallinetti.
The home crowd were then enlivened bythe final score, De Marigny intercepting a pass from Spice for a 60m run-in.
Ospreys coach Lyn Jones:
"This could have been a tricky match for us but we did a professional job, got a bonus point as well as the win, and came away without any injuries.
"As a coach I cannot ask for more than that.
"I was pleased with a number of individual performances, particularly the two young second-rows, and the game was effectively over after half an hour."
Calvisano coach Marc Delpoux:
"We picked up a few injuries on the morning of the game, including our captain Maurizio Zaffiri, and that really affected us.
"We must be honest and accept that we don't have the quality to compete at this level.
"We can try to do our best and we did that today, but the difference is still too big."
Calvisano: Maringy, Gallinetti, Downey, Zanoletti, Tuta-Vodo, Scanavacca, Griffen, Bocca, Intoppa, Cittadini, Bernabo, Ngauamo, Dal Maso, Zanni, Persico.
Replacements: Cagnoni for Gallinetti (71), Pastormerlo for Scanavacca (68), Patelli for Griffen (49), Vigne-Donati for Bocca (43), Ghiraldini for Intoppa (57), Gissing for Bernabo (49), Filippo for Zanni (76).
Ospreys: Byrne, Walker, Parker, Hook, S. Williams, Henson, Marshall, D. Jones, Bennett, A. Jones, A. Jones, Evans, Thomas, Lloyd, Tandy.
Replacements: A. Bishop for Parker (54), Spice for Marshall (54), B. Williams for Bennett (72), Millward for A. Jones (75), Tiatia for Lloyd (41), Bateman for Tandy (64). Not Used: Terblanche.
Referee: P Allen (Scotland)