Sanchez Coello was not the most talented painter when it came to creating large-scale narratives, a fact of which Philip II was aware and therefore looked for Italian trained artists to paint the five larger altarpieces that would show multi-figured scenes. The best known of these was El Greco. El Greco was, as his name reveals, born in Crete in 1541 and died in 1614. His talent as a painter in Crete is documented in 1566, when he was selling paintings there.

In 1568 El Greco went to Italy and his first stop was Venice, although he was in Rome by 1570. It was here that he was introduced to the circle of Count Alessandro Rarnese (nephew to Philip II), by Giulio Clovio, a miniature painter. In this letter he is identified as a disciple of the great Venetian painter, Titian.

Since it is well known that Titian did not have students, no one can be sure of the exact relation between El Greco and Titian. However, the collection of paintings that El Greco painted after 1570 are proof that El Greco did study Venetian artists such as Titian, Tintoretto and Veronese.

In 1576, at the age of 35, El Greco was still in Rome and had experienced no public success, but contacts made in Rome offered him an introduction to potential patrons in Toledo, where he arrived the following year. In 1580 he was commissioned to paint an altarpiece for a chapel dedicated to St. Maurice in the Basilica of the Escorial. He worked on "The Martyrdom of St. Maurice and the Theban Legion" for over two years and received periodic payments that totalled 300 ducats.

El Greco chose to give pride of place to the soldiers positioned in the foreground rather than to the martyrdom, which he placed at a distance on the left. The painting shows the best of El Greco's style, such as the elongated figures and the brilliant colours and fluid brushwork. However, the emphasis placed on the foreground consultation, and the consequent secondary role assigned to the Martyrdom, is thought to have influenced the final decision by Philip II to not display the painting in the Basilica of the Escorial for which it was painted. It was instead housed elsewhere in the monastery and wasn't the first time that El Greco's work had been criticised by his patrons.

El Greco had worked in Toledo for Diego de Castilla, the dean of Toledo Cathedral, who contracted him to paint the "Disrobing of Christ". In his work for the cathedral, El Greco tempered his style, but he overlooked the importance that his patrons placed on the iconography of the scene. Debate about this arose when the work was valued. When it was finished in 1579, representatives of the artist and of the cathedral met to agree on a settlement. El Greco's representatives valued the work at 900 ducats, while the cathedral's representatives claimed it was worth 228 ducats. After two years of debate El Greco accepted 350 ducats and never received another commission by the cathedral authorities. Unfortunately, El Greco's artistic determination clashed too often with the Counter-Reformation orthodoxy of his patrons.

"The Martyrdom of St. Maurice and the Theban Legion" can still be seen today in the Escorial in Madrid. Some of his other paintings are also in Madrid's Museo del Prado, while more of his work is found in museums around the world, such as Chicago, Boston, Washington and Paris.