The money raised from ticket sales benefits the United Way of Central Oklahoma, which established a fund to aid victims of the May storms that killed dozens of people.
A separate benefit concert last month hosted by Oklahoma native country music star Blake Shelton raised more than $6 million in donations and pledges.
Saturday's concert was organized by Keith, who was still playing to a packed house seven hours into the show.
Brooks, who was the biggest draw, took to the stage Saturday afternoon to a rousing ovation.
"Today the healing begins," said Brooks.
Brooks played "Two of a Kind, Workin' on a Full House" and "Papa Loved Mama." His wife, Trisha Yearwood, joined him for a duet, "In Another's Eyes."
"God bless you, Oklahoma!" Yearwood yelled, according to the World.
Some concertgoers said their experiences with tornadoes or someone affected by the recent storms drew them to the fund-raising event.
Marie Carter, a physician whose office is in Oklahoma City, said she watched helplessly as a twister moved through Moore, coming within a half-mile of her own home.
"It was very scary for a lot of us," Carter said, according to the World. "We've been out there helping our friends, digging through the rubble, and because we're so close, we've had a lot of patients come in who lost everything who have symptoms of PTSD. It's almost surreal, but we wanted to come out and support this cause."