A satirical pamphlet in verse, The Ball Room Votaries, involved him in a series of duels, and compelled him to exchange into the 3rd Dragoon Guards, with which he served through the latter portion of the Peninsular War.
In 1819 Dunluce Castle attracted the notice of Thomas Hamilton the original "Morgan O'Doherty" of Blackwood's Magazine, who ridiculed it in a review entitled Poems by a Heavy Dragoon.
In 1821 Quillinan retired from the army, and settled at Spring Cottage, between Rydal and Ambleside, and thus in the immediate neighbourhood of Wordsworth, whose poetry he had long devotedly admired.
He eventually submitted with a good grace, due to the persuasion of Isabella Fenwick, and became fully reconciled to Quillinan, who proved an excellent husband and son-in-law.
In 1843 he appeared in Blackwood as the defender of Wordsworth against Walter Savage Landor, who had attacked his poetry in an imaginary conversation with Richard Porson, published in the magazine.
"Nowhere," says Johnston, speaking of his correspondence during his wife's hopeless illness, "has the writer of this memoir ever seen letters more distinctly marked by manly sense, combined with almost feminine tenderness."
His version of the Lusiad, nevertheless, though wanting his final corrections, has considerable merit, and he might have rendered important service to two countries if he had devoted his life to the translation and illustration of Portuguese literature.