Data stream management system (DSMS) provides convenient solutions to the problem of processing continuous queries on data streams. Previous approaches for scheduling these queries and their operators assume that each operator runs in separate thread or all operators combine in one query plan and run in a single thread. Both approaches suffer from severe drawbacks concing the thread overhead and the stalls due to expensive operators. To overcome these drawbacks, a novel approach called clustered operators scheduling (COS) is proposed that adaptively clusters operators of the query plan into a number of groups based on their selectivity and computing cost using S-mean clustering. Experimental evaluation is provided to demonstrate the potential benefits of COS scheduling over the other scheduling strategies. COS can provide adaptive, flexible, reliable, scalable and robust design for continuous query processor.