Thoroughbred racing dates for 1979 were made official yesterday at a meeting of the Maryland Racing Commission at Laurel Race Course. Officials of Pimlico, the state's most productive track in terms of revenue, were not happy with the commission's decision.

Pimlico traditionally has opened its gates at the beginning or middle of March and run until the end of May or early June. Yesterday's decision has the Baltimore oval opening April 2 and running through June 30.

Other dates: Bowie, Jan. 1 to March 31; Marlboro, (at Bowie) July 2 to Aug. 11; Timonium, Aug. 13 to Sept. 29; Laurel, Oct. 1 to Dec. 31.

By pushing back Pimlico's opening to the beginning of April, the commission forces that track to race into a period that has never been a money maker compared with the earlier dates.

Pimlico part-owner Nathan Cohen said after the commission's announcement, "We got the shaft."

Attorney Richard Case told the commission on Pimlico's behalf: "Pimlico is a finely managed institution. It has air-conditioning and a fine turf course, and its attractiveness to the horsemen and fans is reflected in the attendance and handle.When the three-mile tracks joined to propose the 1979 racing schedule, it, Pimlico, made most of the difficult compromises."

In other business, the commission gave a tentative "yes" vote to the request by Laurel to accept an off-track betting contract offered by New York's OTB. The only possible complications veto of an interstate OTB bill currently on the desk of President Carter and a further request for a larger share of the take from New York.

Adhering to a directive by Acting Gov. Blair Lee, the racing board tacked on 16 racing days to each of the mile tracks' schedules rather than running the 48 dates at one meeting as in the past.