His stage career gained strength in the early 1920s when he became associated with the newly formed Theatre Guild in New York City.

Loeb quickly became a viewer favorite as Jake, the exasperated, loving husband to Berg's meddlesome, bighearted Molly Goldberg.

Loeb denied being a Communist, but the sponsors of The Goldbergs, General Foods, insisted that he be dropped from the show's cast due to his "controversiality".

Loeb was the sole support of a mentally disturbed son, and was burdened with financial problems.

"[8] The following year Loeb committed suicide by taking an overdose of sleeping pills in the Taft Hotel in midtown Manhattan on September 1, 1955.

[citation needed][11] The American Academy of Dramatic Arts—where Loeb was an instructor—awards an annual scholarship in his memory.