Two-time reigning national champion Grassl beat Matteo Rizzo by 20 points in Egna as Ginevra Negrello wins ladies' singles.
Daniel Grassl showed off his quad-jumping skills to complete victory in Stage 2 of the Grand Prix of Italy in Egna.
The 18-year-old had produced unofficial career-best skates to win last month's opening round in Bergamo, but was not quite so impressive on this occasion.
Grassl won by 20 points from PyeongChang 2018 Olympian Matteo Rizzo with Gabriele Frangipani rounding out the podium.
Italian junior champion Ginevra Negrello rose from second place after the short program to take the ladies' singles.
Trailing Grassl by 12 points from the short program, 2019 European bronze medallist Rizzo needed something special to overhaul his young compatriot with his skate to music from 'The Greatest Showman' soundtrack.
The 2019 Universiade winner fell on his opening quad toe loop, having landed on the quarter, but made amends with a slick quad loop followed by a triple flip-triple toe loop combination.
A triple Axel-Euler-triple Salchow was perhaps the highlight of his jumping elements with another triple Axel following.
Rizzo scored 168.63 to take his total to 250.02, a bit down on his personal best of 260.53 achieved at the 2019 World Team Trophy.
Skating to 'Joker' by Cedric Tour, Grassl opened with a shaky quad Lutz - landing on the quarter - before having a hand down on a quad flip.
Then came a much more solid quad loop with the technical element scores from those first three jumps putting him well on the way to victory.
The 18-year-old's jumping was far from flawless, but he avoided serious mishaps and did more than enough to take the win.
Grassl received 176.90 for his free skate, higher than his personal best of 168.27 from January's European Championships although this will not count for record purposes with local judges doing the scoring.
In Bergamo, he scored a massive 189.27 for his free skate largely thanks to stronger execution of those opening three quads.
Nevertheless, his total of 270.38 saw him beat Rizzo by more than 20 points.
Gabriele Frangipani was third with 226.18.
Ginevra Negrello overhauled overnight leader Lucrezia Beccari to take victory in the ladies' singles.
Italian junior champion Negrello was the penultimate skater and landed triple loop-double toe loop and triple toe loop-double toe loop combinations at the start of her skate.
It was a clean routine which earned the 15-year-old a score of 121.13 to take her total to 176.31.
Becarri led by over seven points from the short program, but her jumping let her down in the free skate.
After a solid opening triple flip-double toe loop combination and triple loop, she singled what should have been a double Axel.
Having got back on track, Beccari later under-rotated a triple Lutz before falling at the start of her closing layback spin.
The 16-year-old scored 106.15 for a total of 168.94 and second place.
Elisabetta Leccardi was third with 151.00.