Merlin Olsen, a Hall of Fame pro football defensive lineman with the Los Angeles Rams who was a charter member of the team's famed Fearsome Foursome, then made a remarkably smooth transition into careers in broadcasting and acting, has died. He was 69.

Mr. Olsen died early Thursday at a hospital in Duarte, Calif., outside Los Angeles, while surrounded by his family, his brother Orrin said. He had been diagnosed with mesothelioma, a cancer of the lung lining often linked to asbestos, last year.

Mr. Olsen played 15 seasons in the National Football League from 1962 to 1976, all with the Rams. He was the league's most valuable player in 1974 and appeared 14 times in the Pro Bowl. After retiring as a player, he spent another 15 seasons in broadcast booths as an analyst for NBC and CBS and acted in such television shows as "Little House on the Prairie" and "Father Murphy."

With the Rams, Mr. Olsen helped popularize the star power of defensive linemen sacking the quarterback. The Fearsome Foursome of Mr. Olsen, David "Deacon" Jones, Rosey Grier and Lamar Lundy -- a rare bright spot on mediocre teams from 1963 to 1966 -- used size, speed and skill to terrorize offenses.

"Our philosophy was that they can't double-team all of us," Mr. Olsen said in 1985. "Somebody would be one on one and he'll get the quarterback. There were times, though, when teams would double-team all four or us or change their blocking patterns just to hold us down -- which was a nice compliment."

At 6 feet 5 and 275 pounds, Mr. Olsen was a dominating physical presence, but he also was known for his analytical approach to the game.

"I was amazed by his size just like everybody else but more than that at his great intelligence," former CBS analyst Irv Cross, who played three years with Mr. Olsen on the Rams, told the Los Angeles Times in 1982. "His ability to analyze the game was something everybody on the team recognized. It was just unbelievable that any one person would be gifted in so many ways."

Merlin Jay Olsen was born Sept. 15, 1940, in Logan, Utah, the second of nine children of Lynn Jay and Merle Olsen. He was a three-time academic All-American at Utah State, where he won the Outland Trophy in 1962 as the nation's best interior lineman. He graduated with a bachelor's degree in finance in 1962 and went back to Utah State for a master's in economics in 1970.

Mr. Olsen was the third player picked in the 1962 NFL draft, right after his longtime Rams teammate quarterback Roman Gabriel. Mr. Olsen immediately became a starter, but the team was dreadful, winning only one game in his rookie season.

At first the Rams' coaches weren't sure whether to play Mr. Olsen on offense or defense.

"They put me into a scrimmage at offensive guard, a position I had never played in college," Mr. Olsen told the Times as his career was winding down in 1976. "On my first play, I was supposed to pull and trap Deacon Jones. But just as I came out of my stance, Deacon came across and almost took my head off. I couldn't even breathe for a while. I found out later someone was giving Deacon the snap count. Anyway, I soon moved to defense, where I stayed forever."

The Rams didn't begin winning consistently again until the late 1960s, and despite some good teams during the later part of his career, Mr. Olsen never made it to the Super Bowl as a player.

"That's one goal I didn't reach. But as a professional athlete, I reached or surpassed most every other [goal] a number of times," he told the Salt Lake Tribune in 1994. Mr. Olsen's brother, Phil, was a teammate on the Rams from 1971 to 1974.

Mr. Olsen was elected to the Pro Football Hall of Fame in 1982, his first year of eligibility.

He quickly adjusted to life after football and was best known at NBC for his pairing with Dick Enberg, who used to call the Rams' games on radio.

Mr. Olsen's contract with NBC included the chance to act.

"The first question I asked was where is the training program," he said. "When I found out there was none, I began organizing my own."

He found a willing mentor in actor, producer and director Michael Landon, who cast Mr. Olsen as Jonathan Garvey in "Little House on the Prairie," an adaptation of Laura Ingalls Wilder's books about growing up on the frontier. The former football player seemed right at home portraying a gentle giant.

"Merlin's own character was such that you adapted it to his [television] character," said Kent McCray, producer of "Little House on the Prairie" and "Father Murphy," a series that starred Mr. Olsen as a frontiersman disguised as a priest who was trying to help a group of orphans. "With Merlin, what you saw was what you got. In many instances, it was difficult for him to get mad. By nature, Merlin is not that way. It's impossible to think of him as one of the Fearsome Foursome."

Mr. Olsen's other television series included "Fathers and Sons," and "Aaron's Way." He spent two seasons broadcasting at CBS after NBC hired former San Francisco coach Bill Walsh to replace him as the network's lead analyst.

Mr. Olsen also was a longtime commercial spokesman for FTD.

In December, he was honored at a St. Louis Rams game but was unable to attend. Earlier that month, Utah State announced plans to name its football field after Mr. Olsen.

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