Azaheterocycles are privileged structures due to their presence in natural products, drugs and biologically relevant compounds. Particularly, 1,2,4-oxadiazoles are naturally occurring bioactive molecules, also designated as bioisosteres of amides and esters with enhanced hydrolytic and metabolic stability. More specifically, recent reports suggest the role of 1,2,4-oxadiazolines (4,5-dihydro-1,2,4-oxadiazole) moiety in various biologically active molecules. In this regard, a new method for the synthesis of bi- and tricyclic fused 1,2,4-oxadiazolines has been developed. The process comprises of an oxidative cyclization of corresponding amidoximes in the presence of 2,4,6-tris(4-fluorophenyl)pyryliumtetrafluoroborate [T(p-F)PPT] as the organocatalyst, and molecular oxygen as a green oxidant. Interestingly, T(p-F)PPT acts as electrophilic catalyst and photocatalyst, and the reaction is promoted by visible light irradiation. A metal/base free approach for the straightforward preparation of 1,2,4-oxadiazolines having different functionalities, and high atom economy with respect to the oxygen are the advantageous features of present work. Recent studies on the biological activity of 1,2,4-oxadiazolines offer exciting opportunities in exploring their applications in pharmaceuticals.