Alonso was born on October 17, 1500 at Oropesa in Castile to a noble Castilian family. Educated at the Universities of Talavera and Salamanca, Alonso entered the Augustinian Order at the Convent of San Agustín at Salamanca in 1522 — at the age of 21 — where he received the habit from St. Thomas of Villanova (see his existing entry).
Alonso became the famous Augustinian preacher of the Spanish Golden Age — serving as preacher at the Augustinian Convents of Salamanca, Valladolid, and finally at Madrid.
In 1554, King Philip II appointed Alonso as court preacher — the institutional office of the Spanish Habsburg royal court. Alonso served as royal court preacher until his death 37 years later — producing the Augustinian royal-court preaching tradition of the Spanish Golden Age.
Alonso composed multiple Spanish Golden Age spiritual works — most famously Vergel de oración y monte de contemplación (Garden of Prayer and Mount of Contemplation, 1544), De nueve nombres de Cristo (The Nine Names of Christ), and multiple spiritual treatises that circulated widely in the Spanish Golden Age Catholic literary tradition.
He died at Madrid on September 19, 1591 at the age of 90.