On a night when CBS rolled out the season premiere of “Rules of Engagement” and two franchise reality shows went head-to-head on ABC and NBC, it was CBS that came out on top among the broadcast networks, based on Nielsen overnights.

TVbytheNumbers.com reports that CBS finished Monday night with a 3.1 average rating for prime time in the key 18-49 demo, topping Fox (2.6 average), ABC (2.2) and NBC (1.8). CBS claimed a narrow win in total viewers, averaging 10.1 million for the night to 9.0 million for Fox, 8.1 million for ABC and 4.9 million for NBC.

NBC’s two-hour “The Biggest Loser” came out on the short end of its faceoff with ABC’s two-hour “The Bachelor,” with the NBC reality franchise slipping 13% from last week to a season-low 2.0 in viewers 18-49. “The Bachelor” was also down, slipping 4% to a 2.4.

CBS’s “Rules of Engagement” had mixed results for its season premiere, averaging a 3.1 rating in 18-49 — up a whopping 48% from the 2.1 the show pulled for its season finale in May, but down 14% from its previous season premiere. Meanwhile, CBS’s “How I Met Your Mother” was the top show of the night, delivering a 4.0 average, up 8% from its previous original.

CBS got support from “2 Broke Girls” with a 3.6 in the 18-49 demo and “Mike & Molly” with a 3.1, while “Hawaii Five-0” won the 10 p.m. hour with a 2.3.

The Fox lineup was down, with both “Bones” (2.3 average in 18-49) and “The Following” (2.9) slipping 12% from last week.