Slocum shot a 6-under-par 66 to take a one-shot lead into the final round of the $525,000 Buy.Com Omaha Classic in Omaha, Neb.
Slocum stands at 16-under through 54 holes. Scott Peterson is in second place following a 67. Rod Pampling (69) is two shots back at 14-under.
Overnight leader Jeff Gove is now three strokes off the lead after an even-par 72. Ian Steel is also at 13-under. Steel fired a tournament-low 10-under-par 62 in the third round. Steels day consisted of two eagles and six birdies.
Slocum is vying for a battlefield promotion to the PGA Tour, which is awarded to a player who wins three Buy.Com events in a single season.
Slocum has already won this years Greater Cleveland Open and Knoxville Open
The 27-year-old recorded one eagle, five birdies and one bogey on Saturday at The Champions Club.
Chris Smith (1997) is the only player to earn a battlefield promotion.
Full-field scores from the Buy.Com Omaha Classic