The Montgomery County Office of Economic Developement took advantage of a captive audience of executives attending the Kemper Open Golf Tournament yesterday by giving some of them a 45-minute helicopter tour of the county.

Always looking for ways to bring new business to the county, the OED also placed folders in the hotel rooms of the some 300 executives -- invited to the tournament by the Kemper Group and by local businessmen who are members of the sponsoring Congressional Country Club. OED economic development specialists also will be at the open to try to sell the executives on locating in the county.

The OED, explained Duc Duong; specialist and one of the helicopter tour guides, has no advertising budget, "We had to find a way to reach out to corporate executives," Duong said, "so that's why we decided to capitalize on their presence during the Kemper Open."

The prospect folders hold a map and guide to Montgomery County, full color brochures on possible sites and benefits of locating in the county, a statistical profile, and a special Kemper Open edition of the Washington Business Review, which focuses on Montgomery County.

Sixteen of the visiting executives got the helicopter rides. Those few were invited because they were considered the hottest prospects, Duong said.

The whole package, at a cost of $1,500 to $2,000, was a good investment, according to Duong, when compared to the cost of a full-color page ad in Business Week, which he said costs $35,000.

He added that the county will continue to participate in the Greater Washington Board of Trade "Executours," oganized every two years. according to Duong, the last such areawide tour, in 1978, cost the county only $3,000-$4,000 and brought in at least one business, DataCrown, formerly of Toronto, Canada.