A group of area investors has sued the directors of Action Industries, Inc., charging that the directors failed to tell investors the company was on the rebound when Action offered to buy back 250,000 of its shares for $4 a piece last summer.

That stock, which sold in the $2 to $3 range for more than a year, now is selling for about $20 a share. The investors are demanding either a return of the stock for the $4 they sold it for or the difference between $4 and the current price of the stock.

The investors also are alleging that the directors engaged in racketeering, invoking the provisions of the Racketeering Influenced and Corrupt Practices Act. If a court agrees that the Action directors broke the law and that RICO has been violated, those investors, most of them from Northern Virginia, would be eligible for treble damages. The suit was filed in Federal District Court in Alexandria.

The suit against Action Industries is one of the many ways the provisions of the 1970 RICO Act--designed to attack organized crime's incursions into legitimate business--are being used in situations where organized crime does not exist.

The investors who sued sold back 60,405 shares of the roughly 237,000 shares that were sent back to the company last summer. After the offer, there were about 1.64 million shares outstanding. Five directors of the company owned more than 560,000 of the outstanding shares.

A spokesman for Action Industries--a $65 million company that puts together sales promotions for department stores, said the suit by the area investors is "totally without merit" and that the company "fully disclosed" its situation at the time it offered to buy back some of its shares on July 16, 1982.

Bradley McDonald, lawyer for the 22 area investors, said that his clients allege that Action and its directors violated securities laws in its prospectus describing the stock buy-back and that an official of the Cheswick, Pa., firm misled them again during a phone conversation.

The investors allege that when the offer was made, the company and its directors knew Action would report a profits increase for the year but neglected to tell investors that the prospects for the company were improving.

Shortly after the buy-back was completed on Aug. 6, the firm announced one of the best quarterly earnings performances in its history, the suit alleges.