Upstaging top-ranked playing partner Jordan Spieth in the first round on Thursday.
McIlroy was one stroke behind early leader Henrik Stenson (65) after rolling in eight birdies in his first appearance after two months off, during which he underwent laser eye surgery.
Spieth scrambled well to shoot a 68 but was put in the shade by McIlroy on a warm, wind-free morning. Spieth, who was warned about slow play late in his round, said "it was the Rory that I have seen win majors. It was spectacular."
Stenson birdied five of his last eight holes in his first round after keyhole surgery on his right knee in December.