Kourtney Kardashian exercising on a beach in Miami, Florida with friends on September 27, 2012. Credit: Kadena Press/WENN.com

Kourtney Kardashian is working on her B-O-D in M-I-A.

The reality star, 33 -- who welcomed daughter Penelope, her second child with boyfriend Scott Disick, July 8 -- hit the beach with pals in Miami, Florida Thursday for an intense workout in the sand.

Kardashian didn't expose quite as much as her male companions -- one of whom sported a tiny navy blue Speedo during his exercise session -- though she did show off her toned, lean legs in formfitting, capri-length yoga pants.

Last month, the petite brunette admitted to Us Weekly that she wasn't in any rush to shed her post-Penelope pounds, and that she's more focused on ensuring she eats a nutritious, balanced diet.

"I gained nearly 45 pounds. I'm 5 feet tall, so that's a lot," she shared of her second pregnancy (she's already a mom to two-year-old Mason Disick). But "When I'm here around the house, I just eat healthy," Kardashian told Us. "After I had Mason and was breastfeeding, I craved sweets, so I ate a box of Nilla Wafers a day. But I haven't done that this time."