Treviso did well to keep Ospreys out for much of the first half until Ben John scored, which was the first of four tries in 15 minutes.
And the home side continued after the break as Dafydd Howells, Keelan Giles, Ma'afu Fia, Alun Wyn Jones and a penalty try added to Treviso's early-season woes as they sit bottom of the table.
Ospreys' start is in stark contrast to last season, where injuries and absent players hit them hard, but Tandy insists there is still much work to be done.
"It is just a start. We keep going back to last season and it is like people think we have miraculously found players who had dropped off the face of the earth," Tandy said.
"But there was a World Cup last year and we had 20 players away and picked up a few injuries so it is not miraculous why we have turned it around.
"Olly Cracknell, Rory Thornton and Sam Davies had an indifferent start to last season but they have come through that.
"Those guys have experienced tough learning and it has grounded them. And then you get two Canadian boys for the whole of pre-season.
"The majority of the group we have had for a long time now so it stands us in good stead, but it is only a start."
Fly-half Davies excelled at the Liberty Stadium, as he set up first-half tries for John and Jeff Hassler before making way for Dan Biggar - who made his first appearance of the season following an extended break after Wales' tour to New Zealand.
Biggar is expected to regain the No.10 shirt from Davies, but Tandy is adamant the 22-year-old still has a big part to play and will combine nicely with Biggar this season.
"Sam is doing really well. Let's not forget what Biggs has done in the past so let's not forget him but it is not about one game, it is about the season," he said.
"Sam can't play every game, nor can Biggs and we have to balance that off going to Leinster next week."
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