The sophomore forward hit a career-high five three-pointers to lead the Quakers past Columbia
Cornell's Matt Morgan, who entered the game averaging 24.9 points, was held to 13.
The Quakers, who won their Ivy League opener last week over Princeton, take on the Big Red at the Palestra.
Johnson, the leading scorer in the A-10, missed three games with an ankle injury and came back Saturday but ran out of gas.
The Owls have suffered five straight losses, in all shapes and sizes, including four to start play in the American Athletic Conference.
The Quakers, who placed all five starters in double figures, broke an eight-game losing streak to the Tigers.
The Palestra matchup has been moved back a day because of unsafe travel conditions caused by the recent snow.
Penn opens conference play at home, while Drexel hosts a Charleston team that is tied atop the Colonial Athletic Association
Penn falters in the second half, falling to Toledo, 85-72, and has its four-game winning streak ended.
All but Penn will begin conference play this week. The Quakers have the second-biggest win in the city, behind only No. 1 Villanova.
The Fighting Irish's visit to the Palestra brought McGraw to town for the first time since her induction into the Naismith Basketball Hall of Fame.
Penn senior Caleb Wood knocked down six three-pointers and finished with a season-high 26 points and Ryan Betley picked up his second double-double of the season.
The first-year Villanova big man got going offensively and had the old building shaking in the victory over Penn.