Brown at Northwestern University and the Marine Biological Laboratory (MBL) at Woods Hole, Massachusetts during the summers, he earned his Ph.D. in physiology in 1952.

[2][3] Stephens began his academic career teaching at Brooklyn College (1952–53), after which he joined the faculty of the University of Minnesota (UM) in September 1953.

Some of his most important work during this time period was his 1957 discovery, along with Robert A. Schinske, of the ability of soft-bodied marine invertebrates to take up amino acids and other small-organic molecules directly from seawater.

[4] In 1964, Stephens joined the faculty of the University of California at Irvine (UCI) as the founding chairman of the Department of Organismic Biology.

[5] A man of varied talents, he was a good athlete and proficient amateur pianist occasionally performing as an accompanist for vocal artists at the university.