CBS won or tied for first in all three primetime hours Tuesday, cruising to an easy victory in adults 18-49 and overall viewers.

According to preliminary nationals from Nielsen, CBS’ “NCIS” (4.1 rating/11 share in 18-49, 21.0 million viewers overall) corralled more viewers at 8 p.m. than the programming on the other four broadcast networks combined.

The race drew closer at 9 p.m., but “NCIS: Los Angeles” (3.3/9, 17.3 million) still edged the second hour of NBC’s “The Biggest Loser” in the demo and doubled it in overall viewership. “Biggest Loser” drew 2.9/8, 8.2 million over its two hours, including 3.1/8, 8.6 million from 9 p.m. to 10.

NBC then tied CBS in 18-49 at 10 p.m. with “Parenthood” (2.1/6, 5.6 million), but still trailed the Eye’s “The Good Wife” (2.1/6, 11.3 million) significantly in overall audience.

ABC finished third in all three hours with “No Ordinary Family” (1.8/5, 5.7 million), “V” (2.0/5, 5.7 million) and a special edition of “20/20” (1.3/4, 6.2 million) featuring an interview with astronaut Mark Kelly, husband of shooting victim Rep. Gabrielle Giffords.

Fox was in fourth place over its two hours with a repeat of “Glee” (1.4/4, 4.4 million) and a new episode of “Million Dollar Money Drop” (1.9/5, 5.3 million).

The two-part season (and quite possibly series) finale of “Life Unexpected” (0.8/2, 1.8 million over two hours) was the skein’s most-watched of the season.

Preliminary 18-49 averages for the night: CBS 3.2/9, NBC 2.6/7, ABC 1.7/5, Fox 1.7/5, Univision 1.4/4, CW 0.8/2.

In total viewers: CBS 16.5 million, NBC 7.3 million, ABC 5.8 million, Fox 4.8 million, Univision 3.6 million, CW 1.8 million.