During the quarter, the first of its fiscal year, the company posted an 8.1% year-over-year same-store sales jump. That first quarter performance is an improvement over a 0.4% increase Sonic posted last year. Company officials did warn that same-store sales later in the year will face tougher comparisons, though, because of a stronger performances later last year.

Executives attributed some of the chain's financial success to new products such as the Double Patty Melts, Frito Chili Cheese Wraps, and Philly Cheesesteak Toaster.

The company is also stepping up its national advertising, especially on cable. In 2003, Sonic spent $100 million on marketing, $110 million last year, and the restaurant chain expects to spend $120 million this year. Kansas City, MO-based firm Barkley Evergreen & Partners handles Sonic's advertising.