The Americans picked up six gold medals Thursday and NBC was a beneficiary in primetime as coverage of the London Games racked up huge numbers, peaking with well over 40 million viewers.

Preliminary Nielsen estimates show NBC’s affiliates averaging an 11.2 rating/32 share in adults 18-49 and 35.7 million viewers overall from 8 to 11 p.m., with the night’s final numbers expected to come up some as action extended past 11 o’clock. The primetime portion was up 15% vs. Wednesday night and down some vs. Tuesday, which was the top-rated night of competition so far this summer.

With Thursday’s preliminaries counted, the 2012 London Games are tracking 7% higher than the 2008 Beijing Games in adults 18-49 (11.1/32 vs. 10.4/30) and 14% higher in total viewers (34.9 million vs. 30.6 million) through seven nights. Thursday’s action was highlighted by Gabrielle Douglas capturing the women’s gymnastics all-around event and Michael Phelps collecting his 20 Olympics medal and 16 gold.

CBS was runner-up on the night with encores of “The Big Bang Theory” (1.4/5 in 18-49, 5.5 million viewers overall) and “Two and a Half Men” (1.4/4 in 18-49, 4.8 million viewers overall) followed by an original “Big Brother” (1.9/5 in 18-49, 5.4 million viewers overall), which was down as expected vs. last week but stood as Thursday’s top-rated series in key demos. Closing out the night was a repeat of “Person of Interest” (0.8/2 in 18-49, 3.8 million viewers overall).

Univision, placing third Thursday, again claimed the top series among young adults at 10 p.m. with “La Que No Podia Amar” (1.6/4 in 18-49, 4.2 million viewers overall).

ABC aired a “Wipeout” repeat at 8 (1.0/3 in 18-49, 3.4 million viewers overall) followed by an original at 9 that didn’t fare much better (1.3/4 in 18-49, 3.8 million viewers overall). And at 10, it went with a repeat of “Rookie Blue” (0.6/2 in 18-49, 2.0 million viewers overall), opting to save original episodes until after the Olympics.

Fox aired repeats of “Raising Hope” (0.7/2 in 18-49, 1.9 million viewers overall at 8 p.m. and 0.6/2 in 18-49, 1.7 million viewers overall at 8:30 p.m.) followed by an encore of “Glee” (0.5/1 in 18-49, 1.4 million viewers overall).

Preliminary 18-49 averages for the night: NBC, 11.2/32; CBS, 1.4/4; Univision, 1.3/4; ABC, 1.0/3; Fox, 0.6/2; CW, 0.2/1.

In total viewers: NBC, 35.7 million; CBS, 4.8 million; Univision, 3.5 million; ABC, 3.1 million; Fox, 1.6 million; CW, 0.6 million.