William McKinley Garland Jr., known as Red, was born on May 13, 1923, in Dallas, Texas. His nickname came from his hair color, though sources disagree on whether it was natural or colored. He began on clarinet and alto saxophone and studied with the saxophonist Buster "Prof" Smith, who had earlier mentored Charlie Parker in Kansas City. After joining the U.S. Army in 1941 he was stationed at Fort Huachuca, Arizona, where the Army pianists John Lewis (not the Modern Jazz Quartet's) and Lee Barnes started him on the piano. He was also an amateur boxer, and he lost a bout to Sugar Ray Robinson.

Discharged in 1944, Garland kept teaching himself from the classical exercise books of Carl Czerny and Charles-Louis Hanon and modeled his playing on Count Basie, his early idol. He worked around Texas until 1946, when he joined the trumpeter Hot Lips Page's band; the tour ended in New York in March 1946, and he stayed, finding work there and in Philadelphia. The singer Billy Eckstine hired him for several weeks. In the AllMusic biography, Scott Yanow has him working steadily in New York and Philadelphia from 1946 to 1955 behind Parker, Coleman Hawkins, Lester Young and Roy Eldridge while remaining fairly obscure. A radio broadcast from the Storyville club in Boston on March 10, 1953, with Parker, the bassist Bernie Griggs and the drummer Roy Haynes, was issued in 1985 as Charlie Parker at Storyville.

In 1955 Garland joined the new quintet of Miles Davis, with John Coltrane on tenor saxophone, Paul Chambers on bass and Philly Joe Jones on drums. He and Jones had already recorded with Davis and the bassist Oscar Pettiford for The Musings of Miles on June 7, 1955. Davis was a boxing fan and was impressed that Garland had boxed. The band made its first Columbia recording on October 26, 1955, and its first Prestige quintet session on November 16, 1955, which produced Miles: The New Miles Davis Quintet. To fill out Davis's Prestige contract the quintet then recorded two long sessions at Rudy Van Gelder's studio in Hackensack, New Jersey, on May 11 and October 26, 1956; they yielded four albums, Cookin', Relaxin', Workin' and Steamin', issued between 1957 and 1961. Garland also played on 'Round About Midnight (1957), Davis's first Columbia album. Davis, who had urged him to take on some of the lightness of touch of Ahmad Jamal, was pleased with his style, though some listeners dismissed Garland as a cocktail pianist.

By 1958 Garland and Jones had grown erratic about turning up for recordings and shows, and Davis fired him at one point; Garland is on Milestones, recorded on February 4 and March 4, 1958, with Cannonball Adderley added on alto saxophone. Davis was displeased when Garland slipped a quotation of Davis's own famous early solo on "Now's the Time" into a block-chord chorus on the slower take of "Straight, No Chaser", and Garland walked out of one of the sessions; on "Sid's Ahead" Davis played the piano comping behind the saxophone solos himself. Bill Evans and, from January 1959, Wynton Kelly followed Garland in the Davis piano chair, according to their profiles.

Garland had recorded his own Prestige trio sessions from August 17, 1956, beginning with A Garland of Red with Chambers and the drummer Art Taylor, who anchored his trios through the late 1950s. In November and December 1957 he also led quintet dates with Coltrane and the trumpeter Donald Byrd, which supplied All Mornin' Long, Soul Junction, High Pressure and part of Dig It!. In 1958 he formed his own working trio. He made 25 albums for Prestige and its Moodsville subsidiary between 1956 and 1962 and several more for Riverside's Jazzland label in the early 1960s; the players who joined him on those records included Pepper Adams, Nat Adderley, Ray Barretto, Kenny Burrell, Eddie "Lockjaw" Davis, Jimmy Heath, Harold Land, Blue Mitchell, Ira Sullivan and Leroy Vinnegar.

Rock music cut into the audience for jazz in the mid-to-late 1960s and his record sales fell. He went back to Dallas to care for his mother, and after her death in 1968 he left music for a number of years. He returned to the studio in May 1971 for two albums for the German label MPS, The Quota and Auf Wiedersehen, cut in New York, and later in the 1970s he recorded for Galaxy, Muse, Xanadu and other labels. In 1977 he reunited with Philly Joe Jones for club dates, including a night at the Keystone Korner in San Francisco on May 12 that became Keystones!, and for the Galaxy trio album Crossings, with Ron Carter on bass, recorded that December in Berkeley. He was recorded live in Tokyo in 1978 and 1980 and continued to record until his death from a heart attack on April 23, 1984, in Dallas, at the age of 60.

Garland helped popularize the block chord style, in which both hands sound on every melody note; All About Jazz describes his version as octaves with a fifth added inside in the right hand, over standard modern voicings in the left. He took Nat King Cole and Bud Powell as his main models, with Ahmad Jamal showing in his lighter touch; Count Basie was his early idol and Art Tatum his favorite pianist. Ira Gitler, writing the liner notes for Red Garland's Piano in 1957, praised a direct, warm and buoyant style that was never merely a cocktail-lounge pianist's, and All About Jazz's Joel Simpson singles out his handling of the minor blues and his habit of building a tune slowly. He stayed with standards, show tunes and blues and never moved into modal playing. Critics were not unanimous: Oscar Peterson, commenting in 1961 on "Darling, Je Vous Aime Beaucoup" from Rojo, called the drone-like left hand, punctuated with chords, very monotonous. NPR added A Garland of Red to its Basic Jazz Record Library in 2001, and in Bobby Timmons's profile his trios, alongside Ahmad Jamal's, are credited with shaping that pianist's own group concept.