After receiving his law degree, Rheinschild went to London where he competed for the Illinois Athletic Club in the 1908 Summer Olympics.
 After the Olympics, Rheinschild traveled to Paris, where he claimed to have "taught the 'frog-eaters' how to box for a few months."
 Upon returning to the United States, he got a job "escorting a flock of prisoners across the continent to Mare Island" in Northern California.

In the fall of 1908, Rheinschild served as head football coach for the Washington State University Cougars in Pullman, Washington.
 In his first and only season as coach at Washington State, his football team compiled a record of 4 wins, 0 losses, and 2 ties.
 When the University of Washington claimed to be the football champions of the Northwest, Rheinschild, whose team played Washington to a tie, disputed the claim and challenged them to a rematch in Pullman.
 Rheinschild added, "Can Washington lay claim to the championship over W.S.C. when we played them to a standstill on their own grounds, held them to a 6 to 6 score and were outplaying them in the last 10 minutes of the game, so that nothing but the expiration of time prevented us from scoring a touchdown?"

In 1909, Rheinschild returned to Los Angeles to become head football coach at St. Vincent's College (now known as Loyola Marymount University).
 He led St. Vincent's to an undefeated season and the football championship of Southern California in his one year as head coach.
 The Los Angeles Times praised Rheinschild's efforts in turning the St. Vincent's team into champions:
Rheinschild has accomplished wonders with a squad which at the outset of the season appeared to be mediocre to an unusual degree.
 The Saints' athletic authorities are more than pleased with the success of 'Rheiny.'
 They expected the coach to clean up the Saint athletics and get a start for next year.
 'Rheiny' did considerably more.
 He developed the strongest team the Saints ever had.
 And the eleven played clean ball too.

In 1910, St. Vincent's College withdrew from participation in Southern California intercollegiate athletics, opting to confine athletics to the Catholic student body.

In 1913, Rheinschild was hired as the football coach at Throop College (now known as California Institute of Technology) in Pasadena, California, where he was paid $40 per game—the largest salary ever paid to a football coach in Southern California.
 He continued coaching in the 1910s as the football coach of the Los Angeles Athletic Club.

In 1915, Rheinschild was offered coaching positions at both the University of Michigan and the University of Washington.
 In April 1916 Rheinschild was endorsed to served as the football coach at Occidental College, replacing Joseph Pipal.
 Occidental football records show that Fox Stanton served as the team's head coach in 1916.
 Rheinschild coached at Occidental during the 1917 season.

On Christmas Day 1917, Rheinschild coached and played for a college all-star football team in a match against athletes from the San Pedro Submarine Base.
After receiving his law degree, Rheinschild went to London where he competed for the Illinois Athletic Club in the 1908 Summer Olympics.  After the Olympics, Rheinschild traveled to Paris, where he claimed to have "taught the 'frog-eaters' how to box for a few months."  Upon returning to the United States, he got a job "escorting a flock of prisoners across the continent to Mare Island" in Northern California.
In the fall of 1908, Rheinschild served as head football coach for the Washington State University Cougars in Pullman, Washington.  In his first and only season as coach at Washington State, his football team compiled a record of 4 wins, 0 losses, and 2 ties.  When the University of Washington claimed to be the football champions of the Northwest, Rheinschild, whose team played Washington to a tie, disputed the claim and challenged them to a rematch in Pullman.  Rheinschild added, "Can Washington lay claim to the championship over W.S.C. when we played them to a standstill on their own grounds, held them to a 6 to 6 score and were outplaying them in the last 10 minutes of the game, so that nothing but the expiration of time prevented us from scoring a touchdown?"
In 1909, Rheinschild returned to Los Angeles to become head football coach at St. Vincent's College (now known as Loyola Marymount University).  He led St. Vincent's to an undefeated season and the football championship of Southern California in his one year as head coach.  The Los Angeles Times praised Rheinschild's efforts in turning the St. Vincent's team into champions:
Rheinschild has accomplished wonders with a squad which at the outset of the season appeared to be mediocre to an unusual degree.  The Saints' athletic authorities are more than pleased with the success of 'Rheiny.'  They expected the coach to clean up the Saint athletics and get a start for next year.  'Rheiny' did considerably more.  He developed the strongest team the Saints ever had.  And the eleven played clean ball too.
In 1910, St. Vincent's College withdrew from participation in Southern California intercollegiate athletics, opting to confine athletics to the Catholic student body.
In 1913, Rheinschild was hired as the football coach at Throop College (now known as California Institute of Technology) in Pasadena, California, where he was paid $40 per game—the largest salary ever paid to a football coach in Southern California.  He continued coaching in the 1910s as the football coach of the Los Angeles Athletic Club.
In 1915, Rheinschild was offered coaching positions at both the University of Michigan and the University of Washington.  In April 1916 Rheinschild was endorsed to served as the football coach at Occidental College, replacing Joseph Pipal.  Occidental football records show that Fox Stanton served as the team's head coach in 1916.  Rheinschild coached at Occidental during the 1917 season.
On Christmas Day 1917, Rheinschild coached and played for a college all-star football team in a match against athletes from the San Pedro Submarine Base.
Walter Rheinschild