Johnson turned the ball over five times, including a key fumble that led to a Cowboys touchdown in the fourth quarter and his fourth interception that Lewis returned 28 yards to set up the game-winner.
Brandon Weeden also had turnover problems early, but shrugged them off to throw for 284 yards and two touchdowns as the Cowboys (4-0, 1-0 Big 12) rallied from a 14-point deficit only to let Texas A&M (3-1, 0-1) do the same.
Johnson threw for 409 yards and a career-best five touchdowns but ended up making one mistake too many in a meeting of surging Big 12 South rivals.
Johnson threw two touchdown passes in the final 5 1/2 minutes and had a chance to lead the Aggies on a winning drive of their own before he overthrew a pass into the arms of Lewis, who fell down at the 40-yard line. Oklahoma State picked up 17 yards on two plays before sending on Bailey.
The Cowboys flooded onto the field to celebrate their first three-game winning streak in a series that had been dominated by Texas A&M until recently. The Aggies had won 10 of the first 12 games between the teams following the creation of the Big 12.
After fumbling and throwing two interceptions to help Texas A&M build an early 14-0 lead, Weeden was able to rally the Cowboys in a Thursday night showcase game for the second time in as many tries.
Weeden's first action outside of mop-up duty came while bringing Oklahoma State back from an 11-point, second-half deficit to beat Colorado on a Thursday night last season. That's also the only other time in recent years that the Cowboys wore the black jerseys they sported against the Aggies.
Weeden completed 13 of 15 passes for 184 yards on three scoring drives as Oklahoma State rallied to tie it at 21. Kendall Hunter had a 2-yard TD run in between Weeden's 38-yard scoring pass to tailback Joseph Randle and the tying 29-yard strike to Justin Blackmon.
It was Blackmon's 10th touchdown in four games, the most in the country.
Oklahoma State went up 28-21 after Johnson's third interception of the game led to Hunter's 7-yard touchdown run late in the third quarter.
On A&M's next drive, Johnson dropped the ball, clutched in his right hand, while trying to fight off pressure from Jamie Blatnick. Oklahoma State's Darius Hart rolled on top of the ball, and James Thomas came running up to grab it and race 63 yards to put the Cowboys up by two touchdowns.
Johnson bounced back to lead an 80-yard drive that spanned 7 1/2 minutes, zipping a 4-yard TD pass to Kenric McNeal on fourth down to keep the Aggies alive. Oklahoma State went three-and-out, and Johnson needed just four passes to tie it again on a 28-yard score to Ryan Swope.
Oklahoma State got one first down before punting the ball back to A&M with 1:16 left, and the Aggies were near midfield when Johnson committed his 10th turnover in the past two games -- and it finally cost him.