Whether it is feasible to make your application web browser friendly is a practical question, the answer likely dominated by forces that have nothing to do with COBOL, XML, or xHTML. Feasible can mean worthwhile, a question often usefully directed to accountants.
It is certainly possible to adapt a COBOL application for web browser display. XML and xHTML are both well defined information systems grounded in highly structured text. More than well defined, these systems are exhaustively, minutely, and accurately defined. (Probably better defined than understood.) As COBOL is capable of generating text files, generating XML and xHTML is a task mathematicians call "trivial". ("Trivial" meaning "easy as long as YOU have to do all the work".)
IMHO you have two options. One, learn XML and xHTML. There are plenty of resources, the technology works. Eventually you'll know what a web browser will do, how to do it. (Once you get the hang of it you'll like JavaScript.)
Or two, find someone who already knows XML, xHTML. Show what you have, say what you want, listen.