Thursday’s prime-time overnights offered plenty of bad news for the broadcast networks — especially ABC and NBC. TVbytheNumbers.com reports that ABC’s premiere of “Zero Hour” mustered only a 1.3 average rating in the key 18-49 demo — the worst in-season scripted premiere for ABC in its history. Meanwhile, NBC’s “Community” plummeted eight-tenths of a point from last week to a 1.1, the show’s all-time low.

CBS won the night despite viewer numbers that were mostly down from a week ago. And second-place Fox saw ratings drop for both “American Idol” and “Glee.”

When the dust settled, CBS was on top for prime time overall with a 3.3 average in viewers 18-49, leading Fox (2.7 average), ABC (2.3), NBC (1.5) and Univision (1.5). NBC fell behind Univision in total viewers, where CBS led with 13.8 million to Fox’s 8.7 million, ABC’s 7.6 million, Univision’s 3.7 million and NBC’s 3.5 million.

CBS’s “The Big Bang Theory,” “Two and a Half Men” and “Person of Interest” were all down from last week in the 18-49 demo, while “Elementary” held even. “Big Bang” was the top show of the night with a 5.4 average rating (down eight-tenths), with “Men” coming in second (3.8 average, down three-tenths). “Person of Interest” dipped one-tenth to a 3.0, while “Elementary” again pulled a 2.2.

Fox saw “American Idol” lose a half-point in the 18-49 ratings from last week, settling for a 3.6 average, while “Glee” also lost a half-point, averaging only 1.7.

On ABC the big news was the weak opening for the drama “Zero Hour” at 8 p.m., but that was followed by a bad night for “Grey’s Anatomy” as well — the series sank four-tenths from a week ago to a 2.7 in viewers 18-49, an all-time low for “Grey’s.”

ABC’s “Scandal” held steady with last week with a 2.8 average in 18-49 to win the 10 p.m. hour in the demo.

NBC aired only two hours of original programming, putting up a repeat of “Law & Order: SVU” at 10 p.m. “Community’s” all-time low was followed by a 1.5 in the 18-49 demo for “Parks and Recreation” (down a half-point from last week’s season high) and a 2.0 for a one-hour “The Office,” a slight dip from last week’s 2.1.