NBC didn’t seem to mind the extra competition on the opening night of the season as its Monday tandem of “The Voice” and “Revolution” topped their timeslots in key demo categories.

The shows, which had premiered prior to the start of the season, held up very well opposite all-new program lineups on ABC, CBS and Fox. While NBC more than doubled its opening-night averages from a year ago, surging from fourth to first among the major networks, the other Big Four broadcasters tumbled by 30% or more.

“The Voice” (4.2 rating/11 share in adults 18-49, 11.9 million viewers overall) was easily the night’s No. 1 entertainment series in adults 18-49, handily beating rival reality series “Dancing With the Stars” (2.7/7 in 18-49, 14.6 million viewers overall), which had its weakest premiere scores to date but nevertheless drew the night’s largest overall audience.

In its second week, NBC’s 10 p.m. drama “Revolution” (3.5/9 in 18-49, 11.0 million viewers overall) impressed by retaining about 85% of its very strong premiere score of the previous week, despite the addition of competition last night from returning dramas “Castle” on ABC (2.5/6 in 18-49, 11.4 million viewers overall) and “Hawaii Five-0” on CBS (1.9/5 in 18-49, 8.0 million viewers overall), which was surprisingly low. “Revolution” won easily in 18-49 and 25-54, with “Castle” prevailing in total viewers.

CBS ran second among the broadcasters with pretty good showings by its returning comedies “How I Met Your Mother” (3.4/10 in 18-49, 8.7 million viewers overall), “2 Broke Girls” in its new 9 p.m. timeslot (3.7/9 in 18-49, 10.0 million viewers overall) and “Mike & Molly” (3.0/7, 9.3 million viewers overall) — though the block wasn’t a match for the NBC music contest and each program opened well below their early-season levels of last year. Among scripted programs on Monday, “Mother” drew the night’s top 18-49 share and “Girls” earned the top 18-49 and 25-54 rating.

Not looking as good was the Eye’s new 8:30 p.m. half-hour “Partners” (2.4/6 in 18-49, 6.5 million viewers overall), which sagged between “Mother” and “Girls.”

CBS, of course, was not expected to approach its gaudy opening-night numbers from a year ago, when Ashton Kutcher’s premiere on “Two and a Half Men” drew more than 28 million viewers and propped up the net’s entire lineup. NBC also helped out the competition a year ago by going with low-rated “The Sing Off” and “The Playboy Club.”

Fox’s combo of “Bones” (2.2/6 in 18-49, 7.3 million viewers overall) and “Mob Doctor” (1.3/3 in 18-49, 4.0 million viewers overall) were down from their week-ago premieres, and the latter remains a candidate for the season’s first cancellation.

Last year, Fox aired “Hell’s Kitchen” on opening night (averaging a 2.6/7 in 18-49) and premiered “Terra Nova” the following week.

CW’s lineuo of “90210” and “Gossip Girl” bows on Oct. 8.

Preliminary 18-49 averages for the night: NBC, 4.0/10; CBS, 2.7/7; ABC, 2.6/7; Fox, 1.7/5; Univision, 1.5/4; CW, 0.2/1.

In total viewers: ABC, 13.5 million; NBC, 11.0 million; CBS, 8.4 million; Fox, 5.6 million; CW, 0.5 million.