First-run episodes throughout its Monday night lineup lifted CBS to an easy victory in primetime, though NBC saw encouraging numbers from the season premiere of “The Sing-Off.”

According to preliminary nationals from Nielsen, CBS had the top four performers Monday and five of the top six, winning every timeslot in the adults 18-49 demo and narrowly missing a sweep in overall viewers.

“Two and a Half Men” (4.1 rating/10 share in 18-49, 13.3 million viewers overall) was the top performer for the Eye, followed by “How I Met Your Mother” (3.6/10, 9.4 million), “Mike & Molly” (3.4/8, 11.1 million), “Rules of Engagement” (3.1/8, 8.8 million” and “Hawaii Five-0” (2.7/7, 10.3 million).

Two-hour series “The Sing-Off” (2.8/7, 8.5 million) delivered a record performance for the second-year nonscripted program, improving 22% in the demo over its 2009 debut. “The Sing-Off” also improved NBC’s average in the 8-10 p.m. time period for non-sports programming by roughly 50%, winning Monday in key female demos.

Not so fortunate was the latest outing of ABC’s 90-minute “Skating With the Stars” (1.0/3, 4.8 million), which finished last or tied for last in the demo during its 90-minute run. Against “Skating,” The CW’s “90210” (1.0/3, 2.1 million) and “Gossip Girl” (1.1/3, 2.1 million) matched or beat season-high performances.

Fox also scored tepidly with the “American Country Awards” (1.5/4, 6.0 million), as did NBC’s “Chase” (1.5/4, 5.1 million), which lost nearly half of its “Sing-Off” lead-in. “Chase” recently had its order for its freshman season reduced from 22 to 18 episodes.

ABC saw slight recovery in the second half of its evening with a rerun of “Modern Family” (1.4/4, 4.5 million) followed by a new episode of “Castle” (2.2/6, 8.6 million), which finished second at 10 p.m.

Preliminary 18-49 averages for the night: CBS 3.3/9, NBC 2.4/6, Univision 1.6/4, ABC 1.5/4, Fox 1.5/4, CW 1.0/3.

In total viewers: CBS 10.1 million, NBC 7.4 million, ABC 6.0 million, Fox 6.0 million, Univision 4.1 million CW 2.1 million.