Beche clocked a best lap of one minute 48.171 seconds to head the 11-car LMP2 field ahead of the Status GP team's Lola B12 with Ireland's Yelmer Buurman at the wheel by over three tenths of a second.
British driver Tom Kimber-Smith drove the Greaves Motorsport Zytek-Nissan to third on the grid a further four tenths down, with Guillaume Moreau putting the Oak Racing Morgan-Judd fourth.
Jaime Melo took the GTE Pro category pole on his return to JMB Racing.
The LMP2 class should provide the overall winner following the decision to scrap the LMP1 prototypes in the re-branded series.
The race begins at 12pm local time on Sunday.
1. P2 Beche/Thiriet TDS ORECA-Nissan 1m48.171s
2. P2 Buurman/Sims/Stirling Status Lola-Judd 1m48.482s
3. P2 Ordonez/Kimber-Smith/Brundle Greaves Zytek-Nissan 1m48.882s
4. P2 Nicolet/Moreau/Kraihamer OAK Morgan-Judd 1m48.977s
5. P2 Perez Companc/Bruni/Kaffer Pecom ORECA-Nissan 1m49.068s
6. P2 Firth/Hughes/Moro Murphy ORECA-Nissan 1m49.122s
7. P2 Marroc/Minassian/Sarrazin Loeb ORECA-Nissan 1m49.157s
8. P2 Dolan/Hancock Jota Zytek-Nissan 1m49.687s
9. P2 Frey/Meichtry/Hirschi Race Performance ORECA-Judd 1m50.193s
10. PC Dagoneau/Vignali/Merlin Boutsen Ginion FLM 1m55.338s