Disclosed is a method for producing alkyl tertiary alkyl ethers which comprises reacting t-butanol with an alkanol in the presence of a catalyst which exhibits extended life comprising .beta.-zeolite modified with one or more metals selected from the group consisting of Group IA and Group IIIB of the Periodic Table and continuously contacting said alkanol and t-butanol in a molar amount from about 10:1 to 1:10 over said zeolite catalyst at a temperature of about 20.degree. C. to about 250.degree. C. and a pressure of about atmospheric to about 1000 psig.