WASHINGTON--House Speaker Thomas P. O'Neill Jr. of Massachusetts plays himself in his television acting debut, a five-minute cameo appearance taped for the NBC comedy series "Cheers."

"He knew all his lines perfectly. The man was terrific. The professionalism of the man was unbelievable," publicist Dick Winters of Paramount Television in Los Angeles said yesterday.

O'Neill is in California this week to play in the Bob Hope Charity Golf Classic in Palm Springs and to give several speeches. He taped the "Cheers" segment on Monday.

In the comedy set in Boston, O'Neill ducks into the bar to avoid a woman who tries to tell him her political views and who turns out to be a waitress at the pub.

Inside the bar, O'Neill encounters Norm, the unemployed accountant in the series played by George Wendt. Norm is complaining about how Congress doesn't accomplish anything.

Norm, not realizing that O'Neill is the Democratic Speaker of the House of Representatives, says, "This bozo next to me could do better than that bunch of bums."

"Are you out of work, too?" Norm asks O'Neill.

"No, I'm in the House," O'Neill says.

"Got the wife working, huh?" Norm replies.

O'Neill's appearance was arranged through his executive assistant for 15 years, Delores Snow, whose son, Richard Kolzak, is the casting director for "Cheers".

The logistics for O'Neill's trip to the Paramount studio were worked out Sunday night, and on Monday morning, the executive producers of "Cheers" worked feverishly to write the dialogue.

"They said, 'Action,' he walked in, did a casual lookaround, saw an empty stool and walked over to it. There was nothing false about it," said Winters.

NBC publicist Margo Zinberg said O'Neill's only mistake was that he wrongly tried to open the pub's door. She said O'Neill told them that since the tragic Coconut Grove fire in Massachusetts, a safety regulation in Boston requires that all doors in Boston pull open.

O'Neill's only previous acting appearance was as a butler in a high school play.

Winters said it had not been decided which show will include the O'Neill appearance which will be aired in the teaser that runs before the credits at the opening of the series.

When the taping was over, O'Neill and Wendt, who plays Norm, picked up two glasses from the set and raised them in a toast: "Here's to the Boston Red Sox."

"He was as gracious as anybody I've ever seen I was captivated by the charm of the man Everybody else was too," said Winters.