He is famous as the flamboyant wrestler Hulk Hogan. But today, Terry Gene Bollea was a subdued and sad-faced man as he testified in the Federal trial of his former employer, Vincent K. McMahon, the wrestling promoter charged with illegally providing steroids to the wrestler-performers in his World Wrestling Federation.

Gone were the screaming yellow muscle T-shirt and the manic persona of the charismatic Hulkster. Mr. Bollea, his long blond hair spilling over the collar of a dark business suit, answered questions somberly as the Government tried to show that Mr. McMahon's Titan Sports Corporation had illicitly provided him with anabolic steroids. Defense lawyers, in cross-examination, sought to show that Mr. Bollea's nearly 14-year use of the drugs had been an entirely personal action. Steroid Use Called Common

Prosecutors have charged that Mr. McMahon provided steroids to his wrestlers to build up their physiques and thus make them more appealing to audiences.

Under questioning by a prosecutor, Sean O'Shea, Mr. Bollea, who was testifying under immunity from prosecution, said that steroid use "was fairly common" among wrestlers working for the World Wrestling Federation in the 1980's. He said that while touring for the W.W.F., he would call Emily Feinberg, then Mr. McMahon's executive secretary, "and ask her to place an order for me with Dr. Zahorian." George T. Zahorian is a Harrisburg, Pa., physician who has been convicted of illegally distributing steroids and who has been named as an unindicted co-conspirator in this case. Paycheck, Mail and Steroids