Looking for bargains? How about a portable television set for $40, a chair for $10, a toaster-oven that works for $2? If it sounds good, you should have joined the scores of people shopping from yard to yard in Alexandria's Beverly Hills neighborhood yesterday.

About 20 households trotted out their old junk and fading treasures, turning Tennessee Avenue and Norris Place into the first joint yard sale the people of this middle class neighborhood can recall holding.

"It was a madhouse," said Susan Stone-Helmke, organizer of the event. Her husband, Mark Helmke, said that although the sale didn't begin until 10 a.m., the shady streets were clogged with double-parked cars and eager buyers at 9:30 a.m. Baby clothes, furniture and glassware were big sellers.

Last year, these Saturday merchants might have given their vintage goodies to charitable organizations, several said. But this year, to avoid loading their cars, to make a few dollars and to socialize with their neighbors, they opted for the sale.

They are not alone. Goodwill Industries spokesman Rod Kent said he can't scientifically prove it, but that Goodwill store managers have complained lately that yard sales have cut into their donations. "We do feel a reduction of hard goods--furniture and such," Kent said, adding that clothing sales at Goodwill outlets were especially high last year.

Keith Jones, a spokesman at the national office of the Salvation Army said that garage sales don't seem to be affecting his organization. In fact, he said, this year the group opened a few new thrift stores in the Washington area.

But whether or not the popularity of yard sales is rising, they always seem ubiquitous in the spring. "I never thought about giving up anything" until the yard sale was mentioned, said Mary Ann Warner-Allison, 33, a college instructor and self-proclaimed pack rat. But she and her husband had collected nearly $100 by noon from the sale of an old television, pots and jewelery. "Oh, boy, new shrubs," Warner-Allison said gleefully, counting her profits.

A few doors away, 3-year-old Meredith Haines munched on the brownies her family was selling to shoppers, while her father, John Haines, grumbled that he hadn't sold a pair of old crutches yet.

Chuck Kennedy smiled slightly from his perch on the back of his pickup truck and watched a few husky teen-agers hoist his green vinyl recliner--only $10--into Robin Reese's car. Reese and her neighbor, Ann Hoover, said they had been out all morning "yard-saling."

Hoover, who bought the recliner for her son's room, said she had hit at least 12 sales yesterday, and by 1 p.m. she was ready to go home. "The best buys are gone by now," she said, adding that she does this every spring. "I usually get my winter supply of books for 10 cents each."

Did they find other good bargains? Yes, she said, a complete set of "fine china" for eight--for $15.