Born in New York City, Coco began acting as a child. As an overweight and prematurely balding adult, he found himself relegated to character roles. He made his Broadway debut in Hotel Paradiso in 1957, but his first major recognition was for off-Broadway's The Moon in Yellow River, for which he won an Obie Award. For the next several years he worked steadily in commercials and on stage.
Coco's first collaboration with playwright Terrence McNally was an off-Broadway double-bill of one-act plays entitled Sweet Eros/Witness (1968), followed by Here's Where I Belong, a disastrous Broadway musical adaptation of East of Eden that closed on opening night. They had far greater success with their next project, Next, which ran for more than 700 performances and won Coco the Drama Desk Award for Outstanding Performance. Sixteen years later, the two would reunite for the Manhattan Theatre Club production of It's Only a Play.
Coco also achieved success with Neil Simon, who wrote The Last of the Red Hot Lovers (1969) specifically for him [pictured with Doris Roberts]. It won him a Tony Award nomination as Best Actor in a Play. The two later joined forces for a Broadway revival of the musical Little Me and the films Murder By Death, The Cheap Detective, and Only When I Laugh, for which he was Oscar-nominated.
He worked as a musician in the dramatic movie "Death laid an egg" directed in 1968 by italian director Giulio Questi.
Coco's additional film credits include Ensign Pulver, Tell Me That You Love Me, Junie Moon, Man of La Mancha, Such Good Friends, A New Leaf, The Wild Party, and The Muppets Take Manhattan.
On television, Coco starred in two unsuccessful 1970s series and made guest appearances on many shows, including Marcus Welby, M.D., Fantasy Island, Murder, She Wrote, The Love Boat, and St. Elsewhere, for which he won an Emmy Award. One of his last TV assignments was a recurring role on the sitcom Who's The Boss?.
In his final years, Coco became known for his cooking prowess, publishing several best-selling cookbooks and making frequent guest appearances on talk shows garbed in a chef's hat and apron.
Coco died of a heart attack in New York City in 1987 at the age of 56.