Oster, sent off for the Under-21s in Italy last season, rushed up to push Milan's Massimo Ambrosini after he brought down Andrew Williams after 77 minutes.
The Hungarian referee, Attila Juhof, dismissed the Italian for the foul and Oster, who was left out of the summer tour by Bobby Gould as a punishment for his previous red card, for violent conduct.
The defeat could have been worse but Anthony Williams, the Welsh goalkeeper, saved two first-half penalties from Andrea Pirlo, the first after just two minutes.
Italy went one up after 14 minutes when Alessandro Grandoni forced his way through three half-hearted tackles to crack an angled shot into the roof of the net.
Pirlo missed his second penalty in the 21st minute but four minutes later Italy went 2-0 ahead as Gianni Camandini shot across Williams into the far corner.
In first-half injury-time Simon Haworth was brought down and Bellamy drove in the penalty.
Neil Alexander came to the rescue of Scotland's Under-21 side in Vilnius yesterday, the Livingston goalkeeper making a series of superb saves in a 0-0 draw against Lithuania in a European Under-21 Championship qualifier. He had to ride his luck, however, with the home side twice striking the woodwork in a frenetic second half.
Northern Ireland Under-21s made a losing start to their European Championship campaign when they were beaten 2-0 by a talented Turkish team in Izmit last night.
While Blackburn's Damien Johnson was outstanding for Ireland in what was their first competitive game Turkey deservedly won in the Ismetpasa Stadium thanks to second-half goals from Halit Kobrulu and Erhan Albayrak.