The consultant fired by the Montgomery County executive before finishing a study of the county's Department of Liquor Control said yesterday his own investigation shows that although one brand of liquor had dispoportionate sales in Montgomery, it was not illegally promoted.

Leonard I. Colodny, the consultant, also said he agrees with auditors who said last week the liquor department is mismanaged, resulting in revenue loss to the county, which has a monopoly on sale of alcoholic beverages in restaurants and stores.

The auditors, Touche-Ross and Co., were hired when County Executive Charles W. Gilchrist fired Colodny in August after Colodny charged that Gilchrist's aides asked him to "rethink" figures showing that the liquor department gave a disproportionately large amount of business to Schenley Industries Inc., a New York-based liquor company with ties to the Gilchrist administration.

Colodny said yesterday an investigation he completed on his own shows that sales of Schenley brands were much higher in Montgomery County than in neighboring areas because local restaurant owners bought them out of a sense of debt to Schenley's one-time vice president Charles Buscher.

Buscher, now an unpaid adviser to Ghilchrist on the county liquor department, was a leading proponent of a law narrowly enacted by the Maryland legilature in 1964 that gave Montgomery restaurants the right to serve liquor.

Liquor licensees "ordered Schenley brands because of a longtime association with Buscher and as a show of appreciation . . ." Colodny said. "As far as I'm concerned, this lays to rest favoritism."

Allegations of wrongdoing in the liquor control department arose lst spring after Busher's nephew, a former Schenley salesman, was hired as the department's deputy director.

Colodny said he could find no hard evidence that money could have flowed from Schenley to the liquor department or that liquor licensees were getting illegal discounts from Schenley.

He said the reason there are few low-cost whiskeys on the market in Montgomery to compete with Schenley's J.W. Dant was liquor department mismanagement rather than favoritism.