Harker played his high school hockey at Duluth Denfeld, where he captained the team as a senior.  Following his graduation in 1962, Harker enrolled at the University of Minnesota-Duluth and played one season for the Bulldogs before leaving school to enlist in the United States Air Force National Guard.  Harker served his country from 1963-1965 and then returned to school to finish out his college career.  This time, however, Harker crossed the bridge and played for UW-Superior.  During the 1966-67 season, Harker captained the Yellowjackets to an 8-12-0 record an was voted to the International Collegiate Hockey Association (ICHA).  The Yellowjackets were 23-34-2 in Harker's three years as a player.  His final year (1968-69) he was a graduate assistant coach with Wally Akervik.

Immediately following graduation, Harker entered the coaching ranks when he accepted a postion as an assistant coach at Proctor High School.  Following that one season (1969-70), it was back to Superior where Harker was named the head coach at Superior Senior High School.  Harker spent seven seasons behind the Spartans' bench and enjoyed tremendous success.  He coached the Spartans into the Wisconsin State High School Hockey tournament in each of his seven seasons, in which six of those tournaments they got as far as the championship game.  Harker's teams won three state titles to go along with three runner-up titles and one consolation championship.  Then in 1977, Harker left the Spartans, but continued his coaching career on the same bench, becoming the second head coach in the modern history of UW-Superior.

During his nine-year tenure with the Yellowjackets, Harker coached the Yellowjackets to the NAIA tournament six times, winning a consolation championship in 1980 and a runner-up finish in 1981.  Harker was named the NAIA Coach of the Year in 1980, 1981 and 1982 and coached nine different players (Tom Doig, Mike Baron, Casey VanDamme, Todd Dahl, Don Carlson, Kevin Kranics, Dave Kukowski, Jon Koski and Bob Ritzer) to NAIA All-American selections.  It was this combination of All-Americans, along with a potent supporting cast that made the Yellowjackets one of the most formidable offensive teams in the nation.  And that's not a coincidence, as Harker created his teams with offense in mind.

"I was a very offensive-minded coach," Harker said.  "I was of the belief that fans wanted to see scoring and lots of it."  Harker's teams still hold school records for goals scored in a season (203 in 1978-79).  "It's apparent that I couldn't coach in today's defensive-minded game.  Some people love the 1-0 game, but for me a 5-4 game is exciting for fans and the game itself.  We wanted to try and outscore opponents."

"We played a very high-tempo, high-skill game," current head coach and former Harker forward Dan Stauber said.  "We were always looking for the offensive break, which is directly the opposite of the game today.  We took chances on the power play and penalty kill and defensemen jumped into the rush whenever possible.  In today's game, you only do things like that when the odds are so strongly in your favor that there is no possibility of failure.  It was entertaining to watch and a lot of fun to play that style."

During his years as a high school and college coach, Harker was one of the champions of hockey in the state of Wisconsin.  From 1980-87, Harker provided coaching and instruction for many youth players and coaches through direction and participation in the Superior Amateur Hockey Association (SAHA) player and coaching clinics.  Between 1980 and 1986, Harker also conducted coaching clinics throughout Wisconsin in affiliation with USA Hockey at the intermediate training level.  In addition, Harker served as the head instructor in the Eagle River Recreation Association Annual Summer Hockey Camp for nine years.  It was this dedication to the sport in Wisconsin that got Harker inducted into the Wisconsin Hockey Hall of Fame in 2003.  That induction followed up his induction into the UW-Superior Athletic Hall of Fame in 1998.

Since his departure from the coaching ranks in 1986, Harker has remained in the game and kept himself more than busy.  The only job that might keep a hockey person busier than that of coach is that of scout, and that's where Harker has spent his seasons since 1986.  First with the Ottawa Senators and now with the Los Angeles Kings, Harker has over 15 years of experience of scouting for the National Hockey League.  With over 40 years of experience in sport at the high school, college and professional levels, Gary Harker can be classified as a hockey success and one that UW-Superior is proud to call its own.

Harker also worked for the City of Burnsville as their Director of Recreation.  In December of 2009, the City of Burnsville named the city's rink "Gary R. Harker Rink" in honor of his years of service to the community.

Harker currently resides in Lakeville, Minnesota where he proudly wears the titles of husband, father, father-in-law and grandfather in addition to that of professional hockey scout.

Harker's Coaching Milestones
 
1st Win: 1977 vs. St. Thomas (5-3)
50th Win: 1980 vs. Mankato State (9-5)
100th Win: 1985 vs. St. John's (7-5)