Having four shows on the air at the same time is an accomplishment in itself, but prolific writer-producer Chuck Lorre managed to top that feat last week.

His quartet of CBS comedies ranked among the top 20 primetime programs in adults 18-49 for the Jan. 27-Feb. 2 frame — believed to be the first time a showrunner has pulled this off since the advent of Nielsen electronic ratings measurement in 1991.

The Big Bang Theory,” broadcast television’s No. 1 entertainment series for the season in key demos, ranked fifth for the week in 18-49 (5.2 rating/16 share) — behind only Fox’s four telecasts on Super Bowl Sunday. “Big Bang” was far and away the No. 1 regularly scheduled series in the demo, with CBS’ “How I Met Your Mother” placing second (3.8/11).

Mike & Molly” (2.6 rating/7 share) ranked 11th, and its lead-out on Monday, rookie “Mom,” placed 15th (2.4/6). And at No. 18, in its 11th season, was Thursday’s “Two and a Half Men” (2.0/5).

The four shows, each of which hails from Warner Bros. Television, also made the top 20 in total viewers, led by “Big Bang” (19.05 million).