Coaches are playing Johnson at left tackle to expedite the learning curve, but he'll eventually play both sides.
"The past six months have been crazy," Johnson said. "To go from being the low man on the pole to making the transition, it's really been a blessing."
Gabe Ikard went through a similar transformation, moving from tight end to guard. Ikard said there's one huge difference. Johnson has linebacker-like speed, which will benefit him against speedy defensive ends.
"That kid can fly. He's unbelievably athletic," Ikard said. "He's done a great job doing what he needs to do strength-wise, size-wise to get on the field. He's one of my best friends on the team. We've always eaten together. Now just eats a lot more than he used to."
When he arrived at OU, Johnson weighed 250 pounds. Last spring, he weighed 275. He now tips the scales at 303.
"It's been weird getting used to this new body," Johnson said.
His secret to packing on pounds?
"A half gallon of chocolate milk," Johnson said. "I eat a lot, but chocolate milk has a lot of calories."
Johnson said it's hard to believe three years ago he was a quarterback.
"It's been a shocker," Johnson said. "I've worked my tail off to try and learn the offense... I just want to get on the field and help this team any way I can."