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Cameron Diaz, Gwyneth Paltrow, Nicole Richie, Drew Barrymore

SPW / Splash News

Oh, to be a fly on the wall at this casual girls' night out...

Newlywed Cameron Diaz as well as sister-in-law Nicole Richie and BFFs Drew Barrymore and Gwyneth Paltrow, dined at Katsuya restaurant in Studio City, Calif. on Monday, where the besties enjoyed a fun-filled dinner with two additional pals. 

Richie and Diaz, who are married to twins Joel and Benji Madden, respectively, apparently left their men at home for the evening and opted for a girls' only outing. 

All the ladies were dressed casually for the occasion with the Annie star sporting jeans, flat boots and a printed jacket while Barrymore wore boyfriend jeans, pink heels and an orange coat. Richie, meanwhile, was still rocking her hot pink hair and opted for an all-black ensemble, similar to Gwyneth, although they were both sporting fancy footwear—Richie with leopard print flats and Gwyneth with silver sneaks. 

WATCH: Cameron Diaz is a married woman!

Cameron Diaz, Gwyneth Paltrow, Nicole Richie, Drew Barrymore

Chiva/INFphoto.com

According to an eyewitness, the gal pals arrived at the restaurant around 8 p.m. and stayed for three hours. 

"It seemed like they had a fun night together," the source says adding that Barrymore was "bubbly as always." 

The group left in separate cars after dining at the SBE hotspot—Cameron drove her Tesla with Nicole, while Gwyneth was driven by a bodyguard and Barrymore by a friend. 

The latest sighting of the 42-year-old blond beauty comes just one week after she and her hubby were photographed packing on the PDA at the L.A. Lakers' game when the two were caught on the kiss cam. 

PHOTOS: Cameron Diaz and Benji Madden's road to the altar

Cameron Diaz, Gwyneth Paltrow, Nicole Richie, Drew Barrymore

SPW / Splash News

Benji and Cameron exchanged vows in a whirlwind wedding at Diaz's Beverly Hills estate on Jan. 5 in front of a crowd that included Judd Apatow, Toni ColletteLeslie MannWill Kopelman and Lionel Richie

The loved-up pair tied the knot following a blink-and-you-miss-it engagement (they first stepped out as a couple in May 2014), which occurred just days prior to Christmas Day. 

Both Richie and Barrymore served as bridesmaids during the I-do's, during which about 100 guests gathered to celebrate the 35-year-old Good Charlotte rocker and his beautiful bride. 

"We couldn't be happier to begin our new journey together surrounded by our closest family and friends," the couple told People following the nuptials with a source adding to the publication that Cameron has "truly found happiness."