“Couldn’t stop smiling on set for my new @weightwatchers campaign today! #happy,” she Tweeted.
The native Texan, 33, appears to be channeling her country-girl roots as she wears jeans, a fitted white button-down shirt and cowboy boots.
This latest shot comes just a week after the singer-turned-fashion mogul stunned in a little black dress while on a triple date with fiancé Eric Johnson, sister Ashlee Simpson and her beau, Evan Ross, and best friend CaCee Cobb and her husband, Donald Faison.
Despite her fab figure only four months after giving birth to son Ace Knute, who joined big sister Maxwell Drew, 18 months, Simpson recently made it clear she does not plan to obsess about her weight for the sake of her daughter.
“Raising Maxwell makes me realize that I don’t want her to see me beat myself up for things like food choices or numbers on a scale,” she recently wrote on her Parents.com blog. “Those things don’t determine who we are and instead make us feel terrible about ourselves I want her to know her value, rather than spending her energy fighting negative voices from within.”