IGN's Spence D. noted that "the song is a mixed bag, tossing together slick strings for that orchestrated pop vibe, then mixing that up with a loping, though downplayed, funk groove. It's like two songs in one, though one of the songs feels like a throwback to '80s sterile pop." According to the sheet music published at Musicnotes.com by Sony/ATV Music Publishing, the "girl-empowerment song" has a time signature set in common time, with a tempo of 104 beats per minute. The melody is mainly composed with cinematic strings and features a sitar in the middle eighth, and uses stomping, custom-made beat.
"Beep" received mainly positive reviews from modern critics. When reviewing for PCD, Lisa Haines described "Beep" as a standout tune. Nick Butler from Sputnikmusic wrote that the song may even be better than Don't Cha. "'Beep', [is] pretty much the only thing here that stands up to 'Don't Cha' (it's quite possibly better, actually)."People's Chuck Arnold described the song as "naughty". However Sal Cinquemani from Slant Magazine wrote that the song is a "degrading material".musicOMH's John Murphy described the song as "oddly sexless", "bland", "dull" and "just so damn safe." Senior editor of Billboard magazine, Chuck Taylor described the song as "cliched and overwrought." He ended his review writing "We had higher hopes."
"Beep" debuted at number ninety-three on the US Billboard Hot 100, and eventually peaked at number-thirteen becoming the Dolls' third consecutive top 20 hit, but failed to match the success of its predecessors, "Don't Cha" and "Stickwitu" which both became Billboard top 10 hits. In Canada "Beep" was not a commercial success, peaking at number forty-eight on the Canadian Singles Chart and number forty-five on the Canadian BDS Airplay Chart. In the United Kingdom, "Beep" debuted and peaked at number-two on the UK Singles Chart becoming the Dolls' third consecutive top 3 hit, but spent a relatively short 11 weeks on the chart. "Beep" was also a success in Ireland where it peaked at number-two on the Irish Singles Chart, thanks to the song's success in the United Kingdom. This makes "Beep" the dolls' third consecutive top 3 hit there.
"Beep" was also successful across Oceania. In Australia "Beep" debuted and peaked at number-three for two non-consecutive weeks on the Australian ARIA Singles Chart, becoming the group's third consecutive top 3 hit there also, and was certified Gold by ARIA for sales in excess of 35,000 copies. "Beep" was ranked as the 24th best seller in Australia for 2006, and was one of four songs to have made the Australian ARIA Year-End Singles Chart for 2006 along with "Stickwitu", "Buttons" and "I Don't Need A Man". In New Zealand, "Beep" debuted at number twenty-five on the New Zealand RIANZ Singles Chart, and the following week ascended to its peak at number-one where it spent seven consecutive weeks, becoming the group's third consecutive number-one hit there. "Beep" ended as the year's second best seller, and is the group's most successful single there to date.
"Beep" was also a success in Europe and scored a peak position of number-two on the European Hot 100. "Beep" performed the best in Belgium where it topped the singles chart for a week becoming the Dolls' second number one single there after "Don't Cha". "Beep" was also a success in the Netherlands where it peaked at number-two for two consecutive weeks, becoming the Dolls' third consecutive song to have peaked at number-two following its predecessors, "Don't Cha" and "Stickwitu". "Beep" reached the top 5 in Norway, the top 10 in Germany, Austria, Switzerland and France, and the top 20 in Sweden.
The video (directed by Benny Boom) starts with Scherzinger meeting Will.i.am in an elevator. Will.i.am explains his attraction to which Scherzinger replies by implying she doesn't care about him looking at her. She then enters the Dolls apartment, and, concluding the chorus, they begin a dance routine throughout the second verse. Will.i.am then enters the room, but quickly exits as Bachar throws a bottle of water at him. The Dolls are then seen at a nightclub and a dance break ensues. They are then seen in solo dance spots in front of a large set of speakers. Scherzinger, Bachar and Thornton are seen with Will.i.am, as the video comes to a close. It is also the only song where the chorus is sang by more than one doll, but at separate time. The first chorus features Scherzinger, the second Bacar and the third Thornton.