This year’s March Madness continues to produce strong ratings, with Sunday’s action on CBS up double-digits vs. last year and the overall tournament average at its highest overnight levels in 25 years.

According to Nielsen overnights, Sunday’s Elite Eight doubleheader on CBS averaged an 8.6 household rating/18 share, a 10% increase over last year, and the Saturday/Sunday average of 8.0/16 on CBS and TBS was up 23% vs. last year (6.5/13) and the highest for the regional finals in 10 years.

The Louisville-Michigan State broadcast on Sunday afternoon averaged a 7.6/17 in the overnights — up 17% from last year and the highest rating in the early window in 22 years. The late game between Duke and Gonzaga averaged a 9.9/20 to tie 2010 as the highest rating in the window in 10 years and up 10% vs. last year.

For the entire tournament, its 7.2 overnight rating/15 share was up 11% vs. the same period last year and the highest since the current television format began in 1991.

TBS will carry Saturday’s Final Four semifinals, and CBS will have the championship game next Monday.

In primetime Sunday, NBC’s coverage of the “iHeart Radio Music Awards” (1.7/5 in 18-49, 5.2 million viewers overall) matched the kudocast’s rating from last year when it aired on a Thursday. It won among the major networks in key demos from 8 to 11.

ABC’s “Once Upon a Time” was Sunday’s top-rated scripted broadcast series in 18-49 (1.7/5 in 18-49, 12.5 million viewers overall), followed on the net by “Secrets and Lies” (1.3/4 in 18-49, 5.1 million viewers overall) and “Revenge” (1.0/3 in 18-49, 4.3 million viewers overall). “Once” and “Secrets” both lost 0.2 week to week, and “Revenge” was down a tenth.

Last week’s “Secrets and Lies” rose  by 47% in Live+3 (1.47 to 2.16 in 18-49), with the 2.2 rating a series high for the mystery drama. It could see another sizable lift this week due to the season finale of “The Walking Dead” on AMC and the stronger live programming on NBC.

At Fox, another hourlong “Last Man on Earth” (1.3/4 in 18-49, 3.4 million viewers overall) was down about 25% from last week to its low. It followed all repeats this week, with “Family Guy” doing a 1.2/4 in 18-49 and 2.9 million total viewers at 8:30. Last week, “Last Man on Earth” gained 0.75 in 18-49, going from a 1.77 to 2.52.

CBS had the night’s two most-watched broadcasts with “60 Minutes” and “Madam Secretary,” though preliminary numbers for both shows are murky due to a roughly 15-minute college basketball overrun; the net opted to start all three of its dramas late in most of the country. In the fast affiliate ratings, basketball and “60 Minutes” averaged a 2.8/10 in 18-49 and 14.3 million viewers overall in the 8 o’clock hour. The 8 o’clock hour (“60 Minutes” and “Madam Secretary” did a 1.7/5 in 18-49 and 12.5 million viewers overall. From 9 to 10 p.m., “Madam Secretary” and “The Good Wife” combined to average a 1.1/3 in 18-49 and 9.4 million viewers, and from 10 to 11 p.m., “The Good Wife” and “Battle Creek” averaged a 0.8/2 in 18-49 and 6.5 million total viewers.

Ratings for AMC’s season finale of “The Walking Dead” will be available later today, but the drama is likely to deliver at least four times the number of young adults as any broadcast entertainment program on the night.