CBS’ “Big Brother” dominated in its second night, nearly drawing as many young adults as the combined firstrun offerings on ABC, NBC and Fox during Thursday’s middle hour. The night also saw a fairly good return for ABC’s documentary series “NY Med” and more steady numbers for Fox’s “Gang Related.”

Also of note on the night was best-yet ratings for ESPN’s coverage of the NBA Draft. Its 3.1 overnight rating is up 19% from last year’s 2.6 (which translated to about 3 million viewers in the natoinals) and beat the previous high of 2.7 set in 2003 — the year when LeBron James, Dwyane Wade, Carmelo Anthony and Chris Bosh were all selected.

According to preliminary national estimates from Nielsen, “Big Brother” averaged a 2.3 rating/8 share in adults 18-49 and 6.6 million viewers overall — on par in the demo with Wednesday’s season premiere and up a bit from the show’s initial Thursday installment of last season. If these numbers hold, “Big Brother” figures to claim the week’s top two spots in the weekly 18-49 series program rankings.

The 2.3 for “Big Brother” was nearly equal the combined tallies of dramas “Rookie Blue” on ABC and “Gang Related” on Fox as well as comedy “Undateable” on NBC, each of which did a 0.8 preliminary rating in 18-49.

The night on CBS opened with encores of comedies “The Big Bang Theory” (1.7/7 in 18-49, 7.9 million viewers overall) and “The Millers” (1.2/4 in 18-49, 5.5 million viewers overall) and closed with a repeat of drama “Elementary” (0.7/2 in 18-49, 3.7 million viewers overall). CBS won the night in key demos and total viewers, with “Big Bang” the night’s most-watched program overall.

Fox placed second on the night in 18-49, opening with “Hell’s Kitchen” (1.7/7 in 18-49, 4.9 million viewers overall), which was down a tick in the demo from last week but won its hour in the demo. And at 9, “Gang Related” continues to hang in there (0.8/3 in 18-49, 2.5 million viewers overall), matching its same 18-49 score of the prior three weeks.

NBC opened with a repeat “Hollywood Game Night” (0.8/3 in 18-49, 3.3 million viewers overall), followed by an hour of “Undateable,” with the comedy again earning the same 18-49 rating in both half-hours (this week a 0.8, down from 0.9 a week earlier). And closing things out was “Last Comic Standing” (1.4/5 in 18-49, 3.2 million viewers overall), which rather inexplicably dropped more than 25% week to week; a special firstun “Last Comic” airs Sunday.

ABC is playing out the string of low-rated drama “Black Box” (0.6/2 in 18-49, 3.9 million viewers overall), which drew its lowest score to date and no doubt made life harder for “Rookie Blue” (0.8/3 in 18-49, 4.9 million viewers overall), which was down three-tenths from its two-hour season premiere of last week. And at 10, “NY Med” (0.9/3 in n18-49, 5.5 million viewers overall), built on its lead-in, was competitive in the demo and the timeslot leader in total viewers with its first appearance on the schedule since the summer of 2012 (when it opened to a 1.2 demo rating and the same 5.5 million viewers).

CW did a mere 0.1 rating on the night (about 127,000 adults 18-49) with encores of “The Vampire Diaries” and “The Originals.”

Preliminary 18-49 averages for the night: CBS, 1.5/5; Fox, 1.3/5; Univision, 1.2/4; NBC, 0.9/3; ABC, 0.8/3; Telemundo, 0.7/2; CW, 0.1/1.

In total viewers: CBS, 5.7 million; ABC, 4.8 million; Fox, 3.7 million; NBC, 3.1 million; Univision, 3.0 million; Telemundo, 1.7 million; CW, 0.5 million.