The Interstate Commerce Commission has fired Robert L. Oswald, the former ICC secretary and congressional relations officer who has been a subject of a Justice Department investigation into alleged organized crime influence at the commission.

The ICC said yesterday, the termination, which takes effect in 30 days, "is based on several allegations of impropriety or failure to abide by the commission's Code of Conduct."

Oswald had been placed on administrative leave by ICC chairman Dan O'Neal in June after published reports linked to an investigation by the Justice Department Organized Crime Strike Force headed by John Dowd.

Oswald's deputy, Richard Kyle, was also placed on administrative leave for the same reason. His status remains unchanged.

After being put on leave, both men continued to draw their salaries, Oswald, who has a GS-17 rating, makes $47,500 a year.

Because they were still drawing large salaries, O'Neal decided in September to reinstate them in jobs that were "not of a sensitive nature." according to ICC sources. Oswald was assigned to the managing director's office and Kyle to the Rail Services Planning Office.

But on October 25, Oswald took a combined annual and sick leave.

In a move that surprised many at the ICC, the 43-year-old Oswald then applied for early retirement to the Civil Servie Commission, claiming disab ility.

Yesterday the Civil Service Commission informed the ICC that it would not approve Oswald's application for early retirement.

The Justice Department probe reportedly is aimed at alleged influence peddling at the ICC. According to sources, the probe reportedly centers on members of organized crime - specifically from the "family" of the late Carlo Gambino in New York - who may have influenced decisions at the ICC concerning the proposed merger of trucking interests.

The federal grand jury investigation reportedly also is looking into two mysterious deaths that may be related. In one case, 40-year-old lobbyist Merle Baumgart was killed after his car plunged off a highway into the Potomac River in 1975. The other involved the murder of Alexis Goodarzi, the maitre d'hotel at the Rotunda Restaurant on Capitol Hill earler this year.

Strike Force chief Dowd yesterday would only say that the investigation "is continuing. We are still gathering facts."

Oswald took over the job of secretary in 1970, after his prodecessor. H. Neil Garson, resigned in another scandal. The House Commerce Committee revealed that Garson had falsified account vouchers involving industry-sponsored conventions.

The ICC regulates railroads, bus firms, trucking, inland waterway barge companies and oil pipelines.

Oswald joined the ICC in 1961 as an assistant to the chief hearing examiner, a post he held until 1965 when he left the commission for a year to take a job as administrative assistant to a congressman.

Neither Oswald nor Kyle could be reached for comment yesterday.

The ICC notification to Oswald gives him 15 days to "respond to the allegations."