The Grass Roots, from left: Dennis Provisor, Warren Entner, Rob Grill and Rick Coonce.

Rob Grill, the longtime lead singer and a very nearly original member of the Grass Roots, the immensely popular rock group of the 1960s and afterward, died on Monday in Tavares, Fla. He was 67.

The cause was complications of a head injury he sustained in a fall last month, his wife, Nancy, said. Mr. Grill was a longtime resident of Mount Dora, Fla.

From the mid-1960s to the mid-’70s, the Grass Roots were a fixture on the airwaves and a regular presence on “American Bandstand.” They sold tens of millions of records and had more than a dozen Top 40 hits. Among their best known are “Let’s Live for Today,” “Midnight Confessions,” “Temptation Eyes” and “Two Divided by Love.”

The band’s style married elements of folk-rock, soul, blues and R&B. Its songs, whose close-knit harmonies evoked the British pop groups of the period, were bouncy, accessible and eminently danceable, often backed by an upbeat brass section.

“The Grass Roots weren’t the hippest band on the block,” The Boston Globe wrote in 1989. “But they were — and remain — a sure-fire guilty pleasure, a blissful package of pure pop.”

The group’s longest-serving member, Mr. Grill appeared with the Grass Roots for more than four decades: first in the group’s heyday and again as the band has enjoyed a renaissance on the oldies circuit. His voice — high, sweet and supple — was memorably urgent and beseeching in the group’s many songs of love.

He also played bass and wrote some of the group’s songs, though the Grass Roots’ best-known material was written primarily by nonmembers.

The Grass Roots began life as a phantom. In the mid-1960s, two Los Angeles songwriters, Steve Barri and P. F. Sloan, were asked by their label, Dunhill Records, for songs that would capitalize on the growing appetite for folk-rock.

They wrote “Where Were You When I Needed You” and, as the Grass Roots, recorded a demo. When the song had some success on the radio, they cast about for an existing band to become the Grass Roots.

They enlisted a San Francisco group named the Bedouins, who recorded the first Grass Roots album, also titled “Where Were You When I Needed You.”

In 1967, after the Bedouins decamped, Mr. Barri and Mr. Sloan recruited the 13th Floor, a Los Angeles band comprising Creed Bratton, Rick Coonce, Warren Entner and Kenny Fukomoto. (Mr. Bratton, the lead guitarist, later worked as an actor; he is known for playing the eccentric quality assurance director — also named Creed Bratton — on the American sitcom “The Office.”)

Just as the 13th Floor was about to sign on as the Grass Roots, Mr. Fukomoto was drafted, and Mr. Grill was brought in as a replacement. He remained with the group through the late ’70s, when it faded from view, a casualty of changing popular taste.

Mr. Grill managed new incarnations of the band in 1978 and ’79, rejoining it in the early 1980s. He performed with the Grass Roots throughout much of the ’80s, ’90s and 2000s.

Mr. Grill appeared on many of the band’s albums and also recorded a solo album, “Uprooted,” released in 1979.

Robert Frank Grill was born in Los Angeles on Nov. 30, 1943. Intending to become a lawyer, he studied at California State University, Los Angeles, before pursuing a career in music.

Mr. Grill’s first marriage ended in divorce. Besides his wife, the former Nancy Pilski, whom he married in 1986, he is survived by a brother, James. A son from his first marriage, Christian, died of cancer last year.

Mr. Grill lived for years with chronic pain as a result of a degenerative bone disorder known as avascular necrosis and the multiple hip-replacement operations it entailed. In 2007, he was arrested on charges of having obtained the prescription painkiller oxycodone from multiple doctors, in violation of Florida law.

He entered a guilty plea, which was later vacated after he completed a pretrial intervention program, his wife said.

On the whole, however, Mr. Grill’s life — and the lives of his band mates — was so tame that it became, in some quarters, a professional sticking point.

“I asked one of the guys at VH1’s ‘Behind the Music’ why we weren’t on,” Mr. Grill told The Huntsville (Ala.) Times in 2005. “And he said, ‘Were you guys ever into heroin?’ and I said, ‘No.’ He said we just weren’t compelling enough.”

Robert F Grill