Michael O'Donoghue, a comedy writer who helped create two of his generation's best-known institutions of humor, National Lampoon magazine and the NBC television show "Saturday Night Live," died yesterday in Manhattan. He was 54 and lived in Manhattan.

The cause was a cerebral hemorrhage, said his wife, Cheryl Hardwick.

Friends and colleagues described Mr. O'Donoghue as a comedy trailblazer, with a sensibility characterized by edgy anger at authority and a fondness for bizarre characters and behavior.

He was a lifelong writer whose talents extended to magazine columns, movie scripts and even country songs. Aside from the two Emmy Awards he won as a "Saturday Night Live" writer, Mr. O'Donoghue also achieved a gold record with his song "Single Bars and Single Women," recorded by Dolly Parton.

He and Mitch Glazer wrote the script for the movie "Scrooged." He was also the author of several books, including "TV Zeitgeist" and a book of poetry called "Bears."

Mr. O'Donoghue was born in Sauquoit, N.Y., and attended the University of Rochester. He worked briefly in newspaper journalism before joining Evergreen magazine in the late 1960's. It was at National Lampoon, which he helped start in 1969, that Mr. O'Donoghue found his comic voice, which was aggressive, absurdist and often extremely dark.

After leaving the Lampoon, Mr. O'Donoghue helped create the "National Lampoon Radio Hour," which starred several performers who later transferred to "Saturday Night Live," including John Belushi, Gilda Radner and Bill Murray.

Mr. O'Donoghue was also an occasional performer on "Saturday Night Live." He appeared in the first sketch ever broadcast on the landmark program, in 1975, playing a language instructor teaching English to a confused immigrant played by Mr. Belushi. The sentence Mr. O'Donoghue used to introduce the language was, "I will feed your fingertips to the wolverines."

Mr. O'Donoghue's last work for "Saturday Night Live" was in 1985. In recent years, Mr. O'Donoghue had devoted himself to other writing projects, including a column for Spin magazine called "Not My Fault" and numerous screenplays.

Mr. O'Donoghue is survived by Ms. Hardwick, a music coordinator for "Saturday Night Live"; a sister, Jane Hamilton of Chicago, and his mother, Barbara O'Donoghue.