Southwell began writing poetry in Latin while studying for the priesthood in Rome. Most of his English works were composed between his return to England in 1586 and his capture in 1592. Scholars have had difficulty dating his poetry, while the dates of his prose works are fairly clear. His first full-length English composition, An Epistle of Comfort, to the Reuerend Priestes (1587), began as a series of letters written to the imprisoned Earl of Arundel. The sixteen chapters of the work offer comfort to those persecuted for their beliefs and chastise their persecutors as well as those who have lapsed from their faith. Mary Magdalens Funeral Teares, a meditation on Mary Magdalen's intense feelings and experiences after discovering Jesus's empty tomb, was published in 1591. The Triumphs over Death composed in 1591 and published in 1595, is an elegy on death addressed to Arundel to console him after the premature death of his half-sister. An Humble Supplication to Her Maiestie was a reply to a 1591 proclamation that declared that Catholics were being punished purely for political and not religious reasons. In this work Southwell denies the claims made in the proclamation and argues for Catholics' right to humane treatment. One of Southwell's most popular publications was the handbook A Short Rule of Good Life (c. 1596-97), which contains advice to lay persons about how to live as a Christian. Although none of Southwell's English poems were published during his lifetime, many of them likely circulated in manuscript. In 1595, shortly after his death, fifty-two of his lyrics and his long poem Saint Peters Complaint, were collected in a volume. Another volume of short poems appeared later in the same year under the title Moeoniae. Saint Peters Complaint, written in 132 six-line stanzas, is a dramatic monologue spoken by Saint Peter after his betrayal of Jesus in the courtyard of the High Priest Caiphus. The poem explores the themes of contrition and repentance. Southwell's shorter poetry is also devoted to Christian subjects, explaining humanity's responsibility to respond to revelation with love and atonement. The best known of Southwell's fifty-seven surviving lyrics is “The Burning Babe,” a poem on the Nativity in sixteen lines in which the infant Jesus is depicted as literally burning with a love so intense that even the tears of sorrow he weeps at humanity's rejection of him cannot extinguish its fire. Other well-known poems include “A Vale of Tears,” a look at the conscience-ridden soul; “Christs Bloody Sweat,” about Jesus's agony in Gethsemane; “New Prince, New Pomp,” about the birth of Jesus; and “Upon the Image of Death,” a meditation on death that focuses on the inner state of the narrator.
During his life Southwell's works were published anonymously or circulated in manuscript among a small circle of Catholic believers, but he achieved fame as a writer and religious leader nonetheless. Later, even though Southwell was regarded as a criminal by the authorities, his works began to be sold openly by booksellers. It is likely that William Shakespeare read and imitated Southwell, and Ben Jonson declared that he would gladly have forfeited many of his own poems to have written “The Burning Babe.” For several decades after Southwell's death, his works were widely read and praised for their precision of language, beautiful rhythms, and combination of passion and intellectual analysis. Like many minor poets of the sixteenth century, Southwell's reputation throughout succeeding centuries was overshadowed by that of such masters as Shakespeare and Jonson as well as the great seventeenth-century English devotional poets John Donne and George Herbert. Modern scholarship of Southwell can be said to start in 1935, when Pierre Janelle offered a comprehensive examination of Southwell's life and writing, emphasizing his Catholic humanism and Jesuit neoclassicism. In 1954 Louis Martz, in a critical treatise that argued that seventeenth-century English religious poetry drew its distinctive qualities from spiritual exercises, included what is now regarded as a seminal work of Southwell scholarship. In his essay Martz compared Southwell's work with that of Herbert and Donne and claimed that Southwell anticipated many of the themes and concerns found in later writers, but that his poetry shows him struggling to express these ideas in lyrical fashion. Much subsequent criticism of Southwell's poetry has been indebted to Martz and his assessment of the meditative structure of the poet's verse. Many critics have concentrated on the use of emotion in Southwell's poetry and its themes of contrition and repentance. While most scholars acknowledge the emotional power of the poem “The Burning Babe,” there is general agreement that Southwell's verse is uneven, that some poems are awkward, melodramatic, and unconvincing, while others are written with great simplicity, power, and clarity of thought. In general, modern critics have concentrated on Southwell's poetry, probably because of its more universal appeal; the prose works tend to cover topical events whose details might be lost on modern readers. Nevertheless, Southwell's prose is generally considered to be of consistently high quality, and some critics have maintained that his lucid, well-reasoned arguments and precise language place him among the pioneers of English prose writing. While a few critics have claimed that Southwell's status as a martyr and poet is exaggerated, he is widely regarded as an important historical figure whose poetry at its best presents religious ideas in beautiful and passionate form, and whose prose writings provide insights on the experiences and difficulties faced by Catholics in Protestant England.