Heidi Montag Films 'Summertime Barbie' Segment for 'The Hills'

Here's Heidi Montag wearing a pretty yellow empire-waist dress while shooting scenes for The Hills in Hollywood yesterday.

After sharing lunch and deep conversation with a friend, the reality hottie grabbed her purple bodybag purse and hitched a ride in the Ken-mobile with boyfriend Spencer Pratt.

Looks like we've got some racy material in store for season four...