The first Wednesday post-Olympics produced a ratings uptick for CBS’ ”Big Brother,” which prevailed in the leadoff hour and finished a bit behind NBC’s ”America’s Got Talent” as the night’s top program among young adults.

According to preliminary national estimates from Nielsen, ”Big Brother” averaged a 2.1 rating/7 share in adults 18-49, winning the 8 o’clock hour in all key categories and drawing the top 18-49 share of the night. It was up 11% from last week when it went up against the Olympics for the show’s best Wednesday score of the summer. The net followed up the reality show with repeats of ”Criminal Minds” (1.2/3 in 18-49, 5.4 million viewers overall) and ”CSI” (1.0/3 in 18-49, 5.4 million viewers overall).

At NBC, an encore of ”America’s Got Talent” kicked off the night (1.3/4 in 18-49, 5.5 million viewers overall) and was followed by an original episode (2.2/6 in 18-49, 8.3 million viewers overall), which matched the show’s score for its final pre-Olympics telecast and was Wednesday’s No. 1 show in 18-49, 25-54 (2.7/7) and total viewers. And at 10, a repeat ”Law and Order: SVU” (1.3/4 in 18-49, 4.7 million viewers overall) hit a summer high.

ABC opened with reruns of ”The Middle” (1.0/4 in 18-49, 3.8 million viewers overall), ”Suburgatory” (1.0/3 in 18-49, 3.1 million viewers overall) and ”Modern Family” (1.3/4 in 18-49, 3.7 million viewers overall) and then aired a second ”Suburgatory” encore in its new 9:30 p.m. slot (1.2/3 in 18-49, 2.9 million viewers overall). Closing out the night, and providing the net with time-period improvement over recent slot occupant ”Final Witness,” was a special edition of ”20/20” (1.3/4 in 18-49, 4.1 million viewers overall), which tied with the ”SVU” repeat on NBC as the top broadcast show at 10.

Fox’s ”So You Think You Can Dance” (1.7/5 in 18-49, 4.7 million viewers overall), which aired repeats during the Olympics, matched the average of its most recent original and was Wednesday’s No. 1 show in women 18-34 (2.2/7). Though it ran second in both hours, Fox finished first on the night in 18-49 as lower ratings at 10 p.m. continue to drag down ratings for the Big Three.

At CW, the premiere of musical chairs competition series ”Oh Sit” at 8 p.m. didn’t do great (0.5/2 in 18-49, 1.3 million viewers overall) but is on the high side of the network’s ratings range this summer. In fact, no CW program has done a higher 18-49 rating since the finale of ”America’s Next Top Model” (0.6) on May 30.

Preliminary 18-49 averages for the night: Fox, 1.7/5; NBC, 1.6/5; Univision, 1.5/4; CBS, 1.4/4; ABC, 1.2/4; CW, 0.4/1.

In total viewers: NBC, 6.2 million; CBS, 5.5 million; Fox, 4.7 million; ABC, 3.6 million; Univision, 3.4 million; CW, 1.0 million.