Streelman hit 13 of 14 fairways in regulation and 17 of 18 greens on the Country Club of Jackson layout in Mississippi. He was two strokes in front of Sweden's Carl Pettersson, Ireland's Seamus Power and American Trey Mullinax.
Pettersson holed out from 161 yards for an eagle at the par-four 16th to join the group on 65.
Japan's Hiroshi Iwata, Colombian Camilo Villegas, Canadian Graham DeLaet and former US Open winner Lucas Glover were among a group of seven sharing fifth place a further stroke back on 66.
"Obviously I putted great," Streelman said. "I hit it well.
"I got a little video from my coach, he gave me one or two things to think about today and one of them really clicked," added Streelman, who is in search of his third PGA Tour title and his first since the 2014 Travelers Championship. "I'm just trying to feel a little bit more rotational and not so under – and I was just peppering the flags all day."
