[2][3] In his draft registration card completed in September 1918, Cowles indicated that he was living at Browns Valley and working for his father as a farm laborer.

In his first year as a coach, his Rochester team advanced to the semi-finals of the Minnesota state high school basketball tournament.

[11] In September 1924, Cowles accepted a position as the head basketball and baseball coach at his alma mater, Carleton College.

[12][13] At the time of the 1930 United States Census, Osborne was living in Northfield, Minnesota and listed his occupation as bond salesman.

[22] In his eight seasons as head coach, Dartmouth's basketball teams won the Ivy League championship seven times and finished in second place the other year.

[23] In March 1942, Cowles led Dartmouth to a 47–28 victory over Kentucky to win the East Championship,[23] and the team advanced to the 1942 NCAA basketball tournament title game against Stanford at Kansas City, Missouri.

[23] After 22 months of service, Cowles received his honorable discharge from the Navy in December 1944 and returned to his head coaching duties at Dartmouth in January 1945.

In August 1946, Cowles was hired as the head basketball coach at the University of Michigan, succeeding Bennie Oosterbaan.

The Toledo Blade sports editor wrote:"Win, lose or draw in the red hot scramble for the Western Conference basketball title, the University of Michigan team has done so surprisingly well this season that Coach Ozzie Cowles is getting as much applause on the Ann Arbor campus as came to Fritz Crisler after the football season.

... Those who should know what they are talking about say that Michigan is winning this year, not because of any great supply of sterling cage performers, but because of the personality and coaching finesse of Cowles.

[32] He compiled a 148–93 record at Minnesota, though "he was never able to find the championship touch that he worked at Dartmouth, Michigan and earlier at Carleton College.

At Minnesota, Cowles had a defensive focus, taught "control basketball" and was "often criticized by Big Ten opponents for using a deliberate style of play.

"[39] When Cowles introduced his control-oriented game at Minnesota in 1949, the style was deemed anachronistic and became "the main topic of conversation among net fans in the midlands.

"[40] In February 1949, the Long Beach Press Telegram ran a lengthy feature story on Cowles' strategy.

The article noted:"Ossie Cowles has put the brakes on basketball in the Western Conference, and speculation is rife over whether the hardwood sport has seen the limit, for the time being at least, of the 'fire department' style which sent scores soaring and left fans, players and coaches breathless.

Believing the odds were better, Cowles ordered his team to refuse all free-throws (and instead opt for a jump ball as was permitted under the rules at that time) in a game against Michigan State.

[41][42] Despite losing to Michigan State and being "hooted" by fans, Cowles ordered his players to follow the same strategy in several additional games.

[32] In March 1959, "amid growing anti-Cowles talk among Gopher fans," Cowles resigned his head coaching job at Minnesota.

[43] At the time of his retirement, he ranked among the top 15 coaches in college basketball history, trailing only Adolph Rupp, Phog Allen, Edgar Diddle, Henry Iba, Slats Gill, Fred Enke, Tony Hinkle, Harold Anderson, Jack Friel, Taps Gallagher and Nibs Price.

[43] Cowles was married to Luella Elizabeth Kaus in Saint Paul, Minnesota, at Peoples Church on March 12, 1922.