Bazzana, from Italy, leads the sprint classification by one point over stage winner Jakob Fuglsang of Denmark, and will wear the red leader's jersey for the fourth consecutive day on Thursday as the race flattens out for a 228km leg north to Sonntagberg.
Preidler, from Austria, attacked the first mountain he saw on Wednesday and took maximum points on the first of four categorized climbs in the 141km stage from Lienz.
"I knew that the big climbs up to Gross Glockner and beyond would be a race for the leader's yellow jersey, so I struck early," Preidler said.
With Team Type 1-Sanofi teammate Rubens Bertogliati, Preidler then joined a select group of around 25 riders at the front of the race as the peloton split and the hard climbing began.
Fuglsang went on to a solo victory, in the process taking the yellow jersey and enough points to tie Preidler in the King of the Mountains competition. By race rules, Fuglsang assumes leadership for the KOM prize, but Preidler will wear the distinct white and red polka dot jersey for Thursday's stage five.
Team Type 1-Sanofi General Manager Vassili Davidenko said the KOM competition should get interesting as the Tour of Austria winds its way to the finish in Vienna on Sunday.
"There are no real big mountains left. But every day there will be little chances for somebody to get away and nibble at the lead. Georg showed professionalism beyond his years this morning by attacking the first climb on the Queen Stage, and he will continue to fight for the jersey all the way to the end," Davidenko said
Team Type 1-Sanofi CEO and Co-Founder Phil Southerland said the continued success of the squad in Austria was a terrific inspiration for the global diabetes community.
"We get messages from all over the world from people with diabetes who want to participate in sports and live normal lives. And they do, and they share their knowledge and passion with us, and share in our podium celebrations ever day. To have two riders in leaders' jerseys at the Tour of Austria is a very powerful source of motivation for the diabetes community," Southerland said.
Photos: Mario Stiehl