Ashlee Simpson marked her 21st birthday today (03OCT05) by performing at a Las Vegas lounge as the clock struck midnight.

The PIECES OF ME singer was joined by her sister Jessica Simpson and brother-in-law Nick Lachey at the show, which took place at gambling haven's Pussycat Dolls Lounge.

After the segment was filmed for MTV's ASHLEE SIMPSON LOVE AND LEGAL, the star took her gang to Caesars Palace's Pure Nightclub to party into the early hours of the morning.

Simpson recently admitted that the thing she looked forward to the most about turning 21 was getting the opportunity to gamble legally, explaining, "I used to use my sister's ID, which is really lame. They were like, 'Jessica Simpson... You're Jessica Simpson?' And then I used to have one that said, 'Luanne'.

"But then there came a point where people were like, 'You're not 21 and I know that.'

"People drink like in high school and stuff, but you can't gamble... I don't even know how to play (poker). I don't even care about gambling. I just want somebody to tap me on my shoulder and say, 'Can I see your ID?'"