[2] Channing began the practice of law in Boston, but devoted his attention chiefly to literature.

From 1818–1819 he was the second editor of the North American Review after William Tudor (1779-1830), and remained a regular contributor through much of his life.

From 1819–1850, he taught at Harvard as the Boylston Professor of Rhetoric and Oratory, the position held by John Quincy Adams from 1806–1809.

His students included the noted authors and speakers Ralph Waldo Emerson, Thomas Wentworth Higginson, Oliver Wendell Holmes Sr., James Russell Lowell, Charles Eliot Norton, Wendell Phillips, and Henry David Thoreau.

A memorial volume of his lectures was published in 1856 akong with a memoir of Channing by Richard Henry Dana Jr.