Alumina supported ammonium fluoride was found as an efficient reagent for the synthesis of 1,2,4-oxadiazoles of amidoximes under solvent free conditions using microwave irradiation. This method is a one-pot, easy, rapid, and high-yielding reaction for the synthesis of 1,2,4-oxadiazole derivatives from amidoximes and acyl chlorides. Reaction of amidoximes with acylchlorides in the presence of alumina without ammonium fluoride gave only the corresponding O-acylamidoximes as major product.