McDowell was going into the first turn of his second lap when his No. 00 Toyota got loose, then slammed almost headfirst into the SAFER (Steel and Foam Energy Reduction) barrier. The car ricocheted off the wall and onto its roof, then rolled at least eight times before finally coming to rest at the bottom of the high-banked track.
As he got out of the crumbled car, McDowell waved to the crowd indicating that he was OK.
"I feel great, nothing broke," McDowell said.
McDowell said he had "few little bumps and bruises," but was fine other than that.
He appeared to be slightly limping when he first got out of the car, but he said he felt better after walking around a bit.
He said he was aware of what was going on while his car tumbled down the track.
"I should have, but I didn't close my eyes. I just kind of rode it out," he said. "It wasn't a fun ride, that's for sure. ... I'm fortunate. ... I didn't lose consciousness. I felt every roll down the hill."
While McDowell said he didn't know what happened, he said something "didn't quite feel right" on the car when he came out of fourth turn on the first lap.
"For me to walk away from that wreck is unbelievable," McDowell said. "I'm going to count by blessings and thank God for this opportunity to walk away from that wreck."
Car owner Michael Waltrip had some anxious moments waiting for McDowell to get out of the car.
"Just from the time it stopped flipping until we saw Michael come out, it seemed like forever," Waltrip said. "That was an amazing crash."
Qualifying was delayed for more than an hour while track officials made temporary repairs to the wall. After qualifying, a 20-foot section of the SAFER barrier was replaced.
"With the initial hit and everything that happened after, I'm real happy he walked away," said Carl Edwards, who qualified second in a run before McDowell's accident. "I'm surprised he's not hurt in any way. That's a testament to the safety equipment."
McDowell made his Cup debut last week at Martinsville. A developmental driver for Michael Waltrip Racing, he was promoted to the Cup level to fill a hole in the lineup created when Dale Jarrett retired.
The 23-year-old McDowell had a decent run - he finished 26th - but drew the ire of several veterans for not moving out of the way and holding them up. McDowell has just four career starts in the Nationwide Series, and most of his experience is in ARCA.
Based on owner points, McDowell will start 40th in the backup car for the Samsung 400 on Sunday.