In June, O'Brien transferred to Wisconsin from Maryland, where he made 17 starts the past two seasons and passed for 4,086 yards with 29 touchdowns and 18 interceptions. He graduated from Maryland in May and became eligible immediately at Wisconsin.
O'Brien said Monday that he felt confident in his ability to clinch the spot.
"I think I went into the competition with the mentality that I'm going to start and just kind of focus on myself," he said. "I didn't know when the (starter) was going to be named, and I just wanted to work every day. But I was happy to hear it, but now the work really starts and we've got to move forward."
"Both Curt and Joel had great camps as well, we are very fortunate that we have 3 QB's that can play winning football for us," Bielema tweeted.
O'Brien had two interceptions in a pair of seven-on-seven drills through three weeks of fall camp. That number, coupled with game experience in 17 starts at Maryland, pushed Bielema and assistant coaches in O'Brien's direction.
"The No. 1 thing probably, by far, (was) turnovers," Bielema said. "A lot of those guys were in double digits with turnovers with practice. And then I think just the presence he's shown since he's been here."
O'Brien has two years of eligibility at Wisconsin remaining.
"To be a part of this team is a privilege in itself, but to be named starting quarterback here was something I am proud of just because it's a lot of hard work," O'Brien said. "We have a great quarterback room. It was a really tough competition, a lot of talent in that room, which is awesome and something you want. I'm honored."
Bielema has been impressed with O'Brien's maturity and that he didn't try to "gain all this allegiance with certain player groups," in an effort to win the top job.
Besides a desire to take care of the ball, senior running back Montee Ball said he appreciates O'Brien's work ethic in the locker room and on the field.
"One thing about Danny is that he's learning and willing to help us win," Ball said. "There were three quarterbacks battling hard, playing hard and contributing.
"Whoever steps up to the plate really deserves it. Danny is deserving of the job and will do whatever it takes to help us win."
Information from The Associated Press was used in this report.