The Colossal Cookie Caper began last week at Melwood Elementary School near Upper Marlboro, and in other Talented and Gifted (TAG) programs for fourth, fifth and sixth graders throughout Prince George's County.

The children survey their fellow students, asking what type of cookie they like best. Then they hand a recommended recipe to the cafeteria manager, advertise, sell the cookies and analyze the results.

The children at Melwood found--as students across the county are finding--that no cookie can beat a chocolate chip cookie. But plain chocolate came a close second, so the Melwood students decided to make chocolate cookies with chocolate chips.

"When we took the survey, they wanted hamburger roll size," said 9-year-old Brett Jones. "The biggest was the best."

But a budget-wary cafeteria manager vetoed the idea.

Then the children formed an advertising company called Greatest Advertising Techniques and decided to call their cookie The Greatest American Tempter. (TAG spelled backwards, of course.) They made posters and ran a four-part serial over the school's public address system.

"It's supposed to be like Superman," explained fifth-grader Jeannine Johnson, who helped write the script. The cookies are abducted from Coney Island and taken to Washington. After a high-speed car chase they end up at Melwood, where they are rescued by a heroine called The Great American Tempter.

"Then we killed them," said fellow script writer Nicole Kubick, as she bit into her cookie.

Teacher Nancy Stone said the project made many of her students think about advertising manipulation for the first time. A few Sundays ago, she said, the pastor of the nearby Nazarine Church used a sports figure as an example in a sermon. A student sitting in front of Stone turned around to her teacher and said: "Testimonial." In the next pew, a boy nudged his mother. "Testimonial," he told her.

"Before I was fooled," said Chad Polley, who remembered gettng a race car set he saw advertised as "the best" on television. "One of the cars broke down. It didn't work."

On Cookie Day last week the children sang jingles in the cafeteria, in a last minute barrage of advertising.

The cafeteria staff sold the cookies for 15 cents each. "A suitable price," said fourth-grader Emma Wolford.

So it seemed, for by the end of the lunch period more than 700 cookies had been sold.

And no sooner were they eaten than the TAG group split into pairs and surveyed the children, asking "How did the cookies taste? What did you think of the advertising campaign? What sort of future does the cookie have?"

The children took the completed surveys to the Science Center in Lanham Monday to analyze the results. Medians and means and standard deviation, computers and calculators, and plain old arithmetic were used.

"We're looking for standard devia . . . devia . . . I can't say it," explained 9-year-old Bryan Gay who pored over the figures with his partner David (Buck) Buckingham.

Gay finally did figure it out, and by the end of the day the results were clear: the Greatest American Tempters tasted good. But the advertising blitz didn't affect students' perception of the taste, they found. And they discovered that older students took the whole business less seriously than the younger ones.

"A lot of fifth and sixth graders said they hated it," said Polley, who noted that they wrote "Terrible" on all the survey categories. "Third and fourth graders liked it."

And they also found that their fellow students didn't think the cookies had much of a future. "Strange," science teacher Richard Rubino said. "They liked the taste."

But maybe not so strange. School cafeterias in the county don't normally bake chocolate chip cookies. They are too expensive.