The Masonry Institute has relocated its headquarters from Chevy Chase to the Triangle Towers building on Cordell Avenue in Bethesda. The 28-year-old institute now occupies 1,500 square feet on the building's penthouse level.

The institute said that more than 50 local masonry contractors and suppliers donated money and supplies for the new headquarters, which has extensive masonry work in the reception area and board room.

Other recent developments in commercial leasing in the Washington metropolitan area include:

* Seaboard Foods' Maryland division has leased an egg production facility from DeCoster Egg Farms in Cecilton in Cecil County. The facility currently has three production houses on 300 acres and will expand to eight houses by July 1983. Seaboard expects about 30 new jobs to be created. Seaboard Foods is a subsidiary of Ise America of Japan.

* Small Business Systems, a computer design company based in Manassas, has expanded its operations and leased 3,600 square feet of space at the Indian Creek I Building at the Dulles Industrial Park in Sterling. SBS employs five people at the Sterling location.

* Semi-Systems East Inc., a manufacturer of trailers and fiberglass bodies for vans and trucks, has occupied 5,000 square feet of office and warehouse space at 2401 Old Ox Road in Sterling. The firm employs three people.

* Panache Business Systems Inc., a new computer hardware and software sales and service company, has located in Bluemont, Va. Panache employs eight people.

* American Satellite Corp. has leased 19,000 square feet of space at the Research Boulevard Center II building in Gaithersburg.

* The Great Foodini Inc., a restaurant chain that offers entertainment, has leased space for locations in Rockville and Fairfax. In Fairfax, the Great Foodini will occupy 9,500 square feet in Fair Oaks Mall. The Rockville location will occupy 10,200 square feet at a location on Rockville Pike near Montrose Road.