Biffle drove down into Turn 3 and charged under Johnson with 30 laps remaining Saturday night, then pulled away to end his 49-race winless streak while giving owner Jack Roush another NASCAR Sprint Cup victory in Texas.
"I just dug deep. I knew I had to do it and kept trying and trying and trying," Biffle said. "I knew the team would forgive me if I wrecked it trying to beat him so I just gave it all I had."
Once Biffle got his No. 16 Ford around Johnson, he went on to a 3.2-second victory in the fastest Cup race in Texas with an average speed of 160.577 mph.
"Catching the 48 at the end, it was all I had to be able to get to him," he said. "It seemed like when we got to him, it was too easy."
Biffle's 17th career victory was his first since an October 2010 race in Kansas, where the series goes next week.
Johnson led three times for 156 of the 334 laps while going for owner Rick Hendrick's 200th victory. But he never recovered, even scraping hard into the wall trying to catch up after Biffle drove under him and completed the pass before the start-finish line.
It was Roush's ninth win in 23 Cup races at Texas, and completed a Lone Star State weekend sweep. Ricky Stenhouse Jr. won the Nationwide race on Friday night for Roush's fourth Texas victory in a row and ninth overall in the second-tier series.
"I don't know if this is my last sweep," Roush said. "But I'm going to remember this one for a long time."
After starting third, season points leader Biffle was among the lead pack the entire race, leading 90 laps on a fast-paced and windy night.
There were only two cautions for 10 slowed-down laps, both for debris, and the race finished with a record 234 consecutive laps of green-flag racing.
Biffle said his hands were hurting from fighting the wheel through the wind. But he thought there were no major incidents because every driver was dealing with the same conditions and maybe more cautious because of them.
Mark Martin finished third in a Michael Waltrip-owned Toyota, followed by Jeff Gordon and Roush driver Matt Kenseth. Polesitter Martin Truex Jr., another Waltrip car, was sixth after leading 69 laps.
Biffle got his eighth consecutive top-10 finish at Texas, where he had a victory in 2005 even before that stretch.
He was surprised that it was so easy after the final pass gave him his seventh and last lead in the race.
"I thought he was going to be right there," Biffle said.
Said Johnson, who had led 119 laps combined his first 17 Texas races, "He got by me and I was chasing him from there. I didn't have anything left to go get him. I tried."
For Hendrick Motorsports, it was another close call for its first victory of the season and the owner's 200th in a career that began in 1984.
Johnson, Gordon and teammate Dale Earnhardt Jr. were running in the top three at Martinsville two weeks ago before a late restart in the last race before the Easter weekend break. But Clint Bowyer's aggressive inside move took out Johnson and Gordon, and Earnhardt ended up third.
"It's nice to be running well. It's nice to be in this position," Johnson said. "But I want to get back to our winning ways really soon."
Kasey Kahne, the first-year Hendrick driver, finished seventh ahead of another Roush driver, Carl Edwards. Harvick and Earnhardt rounded out the top 10.
The first lead change came on the 32nd lap when Biffle went around the top through Turns 1 and 2 and got past Truex on the backstretch.
Five laps later, Kenseth went around the outside of Truex through Turns 3 and 4 to take over second place.
The first caution flag came out on lap 67, when a cap was tumbling around near Turn 2 on a night when the wind was gusting more than 30 mph.
Gordon, who started 34th, was in the top 10 before the second caution after Trevor Bayne scraped the wall.
The race restarted on lap 100, with Truex in front of Biffle for only one lap. There were no more yellow flags after that.