Acting in a Canadian production of "Shenandoah" proved a fortunate move for the actor, who ended up making his Broadway debut when the musical revival landed on Broadway in 1989. 1991 saw Cavanagh take a regular turn on the Canadian series "No Place Like Home", and that same year he appeared in the 1991 Canadian independent feature "White Light".

Appearances in the Canada-lensed 1993 TV-movies "1994 Baker Street: Sherlock Holmes Returns" (CBS) and "Other Women's Children" (Lifetime) marked the beginning of the actor's US credits. He was featured in the Canadian family adventure "Magic in the Water" (1995), starring Joshua Jackson, and racked up more TV-movie credits that same year in "A Vow to Kill" (USA Network) and "Dangerous Intentions" (CBS). As he slowly built up recognition with small roles in the United States, to those north of the border he was instantly familiar as the star of a popular series of clever beer commercials for Labatt's. Cavanagh proved himself further to the Canadian audience with a turn in the romantic comedy "Honeymoon" (1997), impressing with his supporting performance as a man ruled by his libido. Other Canadian independent film credits included "Something More" (1999), which co-starred the actor as a charming but somewhat spineless insurance agent.

While his numerous TV-movie credits and independent film appearances didn't mark him as a breakout star, Cavanagh landed a starring role the promising Fox pilot "The 900 Lives of Jackie Frye" (1998), which disappointingly never aired. He recovered with a recurring role on "Providence", playing Doug 'Dog Boy' Boyce, an obedient and oddly canine employee who assisted Joanie (Paula Cale) at her pet bakery. Through interaction with Joanie, the endearing Doug became increasingly human, and eventually departed the Rhode Island city to follow his dream. A memorable role in a popular show would help Cavanagh to launch "Ed", a quirky comedy-drama set in small town America. Cavanagh starred as Ed Stevens, a former New York City lawyer who loses his job and catches his wife in an extramarital fling on the same day. With nothing left to lose, he moves back to his hometown, rekindles his not-so-unrequited love for high school crush Carol Vessey (Julie Bowen) and buys a bowling alley. "Ed" was a surprise hit with audiences, due in no small part to Cavanagh's unique self-effacing charm and talent for making the somewhat goofy character irresistible.