Because he was seen as more of a personality, Reilly found few outlets in features: he debuted in a small role in the superb "A Face in the Crowd" (1957) but was virtually wasted in the uneven musical "Two Tickets to Paris" (1962). By the time he was an ascendant Broadway player, he found more opportunities in TV. After a brief run on the short-lived variety series "The Steve Lawrence Show" (CBS, 1965), Reilly found a niche as the modern-day descendant of a sea captain whose spirit is haunting a rental property in the sitcom version of "The Ghost and Mrs. Muir" (NBC. 1968-69; ABC, 1969-70). He went on to become a frequent guest on "The Dean Martin Show" and hosted the 1970 NBC summer variety program "The Golddiggers in London". Throughout the next decade, he lent his unique presence, wicked wit and sense of humor to a variety of roles, including the evil magician Who Doo on the kids' series "Lidsville" (ABC, 1971-73; NBC, 1973-74) and the titular host of the spoof "Uncle Croc's Block" (ABC, 1975-76). Simultaneously, Reilly delighted fans as a panelist on "The Match Game" (CBS, 1973-79).

While he had begun to gravitate to the director's chair in the 60s, Reilly achieved a breakthrough with his staging of the one-person play "The Belle of Amherst" (1976), with Julie Harris portraying poet Emily Dickinson. He and Harris would go on to collaborate as director and star on over ten more productions spanning some twenty years, culminating in the 1997 Broadway revival of "The Gin Game" for which both earned Tony nominations. The busy hyphenate (who could make a case for the title as one of "the hardest workers in show business") managed to squeeze in time to teach at both the HB Studios in NYC and the Burt Reynolds Institute in Florida. A personal friend of Reynolds, Reilly also acted with his pal in the film "Cannonball Run II" (1983) and helmed episodes of the CBS sitcom "Evening Shade" in the early 90s.

Another turning point for the actor came in 1996 when he was tapped to create the character of author Jose Chung in a memorable episode of Fox's "The X-Files". Appearing without his trademark toupee, Reilly reminded audiences that he was a capable actor. The success of that particular performance led to a string of guest appearances and a film with Julie Harris and Joe DiMaggio ("First of May" lensed 1997). He reprised the character of Jose Chung for laughs in a little-seen episode of the CBS sitcom "Meego" and again to much greater effect in an segment of Fox's "Millennium". The latter performance netted him a 1998 Emmy nomination as Best Guest Actor in a Drama Series. The following year, he earned his third Emmy nomination for a guest appearance on the ABC sitcom "The Drew Carey Show".