Tim Clark and Tom Pernice Jr. finished their third rounds Sunday morning and joined Beem at 19-under-par 197 to share a one-stroke lead heading into the final round, which was scheduled to begin later in the morning with the leaders teeing off at 11:00 a.m. (ET).
Beem fired a 9-under 63 in his third round to reach the score, while Clark and Pernice shot a 66 and 68, respectively, in their rounds.
The trio leads a group of four players tied for fourth place at 18-under-par 198. Among them is second-round leader Carl Pettersson, who managed just a 1-under 71 in his third round. Mark Wilson (63), Mark Calcavecchia (65) and Geoff Ogilvy (68) are also at minus-18.
The tournament has faced weather issues since Friday. Rain showers are forecast for Sunday morning and thunderstorms are expected later in the day.
Other than the weather, the big story this weekend was Tiger Woods missing his second cut of the season and third of his career.
The world's No. 1 golfer needed to finish birdie-birdie at the conclusion of his second round Saturday morning, and instead closed bogey-par to miss the cut by three strokes at minus-three. World No. 2 Vijay Singh also finished on the outside looking in.
Sharing eighth place at 17-under-par 199 after three rounds were Justin Rose, who fired a 64 in his third round, and Harrison Frazar, who shot a 66. Lucas Glover (66) and Kent Jones (70) are tied for 10th place one stroke further back.
Defending champion Ryan Palmer was also in the mix, finishing 54 holes at minus-13 to share 21st place with seven other players.