Bruce was born on the 2nd of June 1934, in Spokane, Washington, and he graduated from North Central High School in 1952. He went on to Spokane Technical School and Eastern Washington State College before enlisting in the US Army on the 17th of August 1954. Bruce was stationed at Fort Ord and Fort Lewis until his discharge in 1957, returning to Spokane and getting married. By November of 1961, he had two daughters and reenlisted into the Army and returned to Fort Lewis. He completed the Airborne School at Fort Benning and served two tours in Korea before being assigned to the 4th Infantry Division at Fort Lewis. By the fall of 1966, Bruce deployed with 1st Battalion, 8th Infantry, 4th Infantry Division in support of the Vietnam War and it was his actions on the 18th of May 1967, that would later earn him the Medal of Honor. The citation reads:

For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty. P/Sgt. Grandstaff distinguished himself while leading the Weapons Platoon, Company B, on a reconnaissance mission near the Cambodian border. His platoon was advancing through intermittent enemy contact when it was struck by heavy small-arms and automatic-weapons fire from three sides. As he established a defensive perimeter, P/Sgt. Grandstaff noted that several of his men had been struck down. He raced 30 meters through the intense fire to aid them but could only save one. Denied freedom to maneuver his unit by the intensity of the enemy onslaught, he adjusted artillery to within 45 meters of his position. When helicopter gunships arrived, he crawled outside the defensive position to mark the location with smoke grenades. Realizing his first marker was probably ineffective, he crawled to another location and threw his last smoke grenade but the smoke did not penetrate the jungle foliage. Seriously wounded in the leg during this effort he returned to his radio and, refusing medical aid, adjusted the artillery even closer as the enemy advanced on his position. Recognizing the need for additional firepower, he again braved the enemy fusillade, crawled to the edge of his position, and fired several magazines of tracer ammunition through the jungle canopy. He succeeded in designating the location to the gunships but this action again drew the enemy fire and he was wounded in the other leg. Now enduring intense pain and bleeding profusely, he crawled to within 10 meters of an enemy machine gun which had caused many casualties among his men. He destroyed the position with hand grenades but received additional wounds. Rallying his remaining men to withstand the enemy assaults, he realized his position was being overrun and asked for artillery directly on his location. He fought until mortally wounded by an enemy rocket. Although every man in the platoon was a casualty, survivors attest to the indomitable spirit and exceptional courage of this outstanding combat leader who inspired his men to fight courageously against overwhelming odds and cost the enemy heavy casualties. P/Sgt. Grandstaff's selfless gallantry, above and beyond the call of duty, are in the highest traditions of the U.S. Army and reflect great credit upon himself and the Armed Forces of his country.

Bruce, referred as Platoon Sergeant, was an E-7 Sergeant First Class and was 32 years old when he died. His family received his Medal of Honor from President Nixon on the 10th of July 1969, in a private ceremony at the White House. Bruce Alan Grandstaff is buried in the Greenwood Memorial Terrace in Spokane, Washington: Honor Section, Lot 1540, Space 7. His name appears on the National Vietnam Veterans Memorial in Washington DC: Panel 20E, Line 28.