Merrill Lynch, Pierce, Fenner & Beane, the country's largest investment house and the author of such innovations as evening office hours for securities firms, will put part of its business on wheels. The company has ordered three specially designed buses to operate as mobile branch offices in 15 suburban communities around Chicago, Boston, and Newark, N. J. Homer P. Hargrave, managing partner in Chicago, said the Chicago unit will arrive in town between April 5 and April 10. It will be on exhibit in the Lydy parking lot on La Salle St. across from the Board of Trade building for several days before it starts on its scheduled runs.

Once it begins to travel its regular route the bus will be in Hammond on Mondays, Gary on Tuesdays, Indiana Harbor on Wednesdays, Waukegan on Thursdays, and Evanston on Fridays, Hargrave said. Arrangements have been made for the bus to be parked in the same location in each town each week.

Each bus will contain a boardroom where stock prices are posted and two private offices where investors or potential investors may talk with Merrill Lynch account executives. The buses will be equipped with radio-telephones tied in directly with the firm's private wire system, making market quotations available on an up to the minute basis.