Fox rolled to another Tuesday victory behind dominant showings by “American Idol” and “House,” according to preliminary nationals from Nielsen. CBS was second with the “40th Annual Academy of Country Music Awards.”

In the night’s opening hour, “American Idol” (10.1 rating/29 share in adults 18-49, 24.4 million viewers overall) towered over the competish, matching the 18-49 delivery of the other five broadcast nets. The WB’s “Gilmore Girls” had a solid outing with its season finale (2.3/6 in 18-49, 5.6 million viewers overall), placing second to Fox among adults 18-34 and young women.

Fox kept rolling at 9 with “House” (7.0/18 in 18-49, 17.7 million viewers overall), and NBC’s “Law & Order: Special Victims Unit” won at 10 (5.5/14 in 18-49, 15.8 million viewers overall).

At CBS, the “ACM Awards” (3.7/10 in 18-49, 11.8 million viewers overall), the best demo delivery for the kudocast in three years. And for ABC, expanded episodes of comedies “My Wife and Kids,” “George Lopez” and “According to Jim” averaged a 2.6/7 in 18-49 and about 6.8 million viewers overall from 8 to 10.

Also on the night, UPN attracted some initial curiosity for limited-run series “Britney & Kevin: Chaotic” (1.8/4 in 18-49, 3.5 million viewers overall). Its premiere improved by about 80% upon the 18-34 delivery for the season finale of “Veronica Mars” one week earlier.

Preliminary 18-49 averages for the night: Fox, 8.6/23; CBS, 3.7/10; NBC, 3.4/9; ABC, 2.4/6; WB, 2.1/5; UPN, 1.5/4.

In total viewers: Fox, 21.0 million; CBS, 11.8 million; NBC, 10.2 million; ABC, 6.5 million; WB, 4.9 million; UPN, 3.1 million.