The blond bombshell looks radiant and is positively glowing, grinning widely and sporting a formfitting white dress shirt, skinny jeans, brown boots and a matching belt. Her long locks are down and she is standing in a field.
"Couldn't stop smiling on set for my new @campaign today! ," the 33-year-old captioned the pic.
"We were thrilled to welcome Jessica back on the Weight Watchers program in August," Weight Watchers said in a statement in September. "With a toddler on the run and an infant to look after, we know she needs a plan that's simple and fits into her life along with the support that's so important to moms with young children."
Just last week, Simpson showed off her enviable figure in a sexy LBD, along with her fiancé Eric Johnson, sister Ashlee Simpson and her boyfriend Evan Ross, BFF CaCee Cobb and her husband Donald Faison, during a triple date night.
The singer recently opened up in a guest blog post on Parents.com about her pregnancy weight gain, writing candidly about body image and what she wants her 17-month-old daughter, Maxwell, and 4-month-old son, Ace, to learn from her.
"My pregnancies (especially my first with Maxwell) were well documented and my struggles with my weight and body image have played out in front of the world," Simpson wrote. "As hard as that has been, the hardest part is to realize that with all the hurtful and harsh criticism from others, I have been the hardest on myself."