Edward de Vere Earl of Oxford was 33 in 1583, when Queen Elizabeth’s company of adult actors was formed by the direct order of Sir Francis Walsingham, head of the government’s intelligence operations, just as the war between England and Spain was becoming official. During the next crucial years, leading up to the victory over King Philip’s armada in 1588, the new company would perform at Court in winter and then in summer divide into two traveling troupes. With its actors wearing the Queen’s livery representing Her Majesty and the Crown, the wartime company staged anonymous plays of English royal history to promote patriotic loyalty and unity.
During the 1580’s the Queen’s Men performed works that “Shakespeare” would later turn into mature plays such as King John, Richard III, 1 Henry IV, 2 Henry IV, Henry V and King Lear; and the record shows that Lord Oxford and John Lyly, his private secretary and stage manager, were closely connected to the Queen’s Men from the outset. When put together, these two facts provide strong evidence that the author of the earlier works performed by the Queen’s Men was Oxford himself, and that it was he who revised his own previous plays for which”Shakespeare” would get the credit.

"The True Chronicle History of King Leir" -- acted by the Queen's Men in the 1580's, published in 1605, and the principal source of Shakespeare's "King Lear"
Oxford had returned from Italy in 1576 and it appears that he proceeded to write plays that were brought to the royal court by the Children of St. Paul’s and by his friend Thomas Radcliffe, 3rd Earl of Sussex, who was a kind of father figure to him. [Oxford had served with him in the military campaign of 1570 against the northern Catholic earls in rebellion against Elizabeth.] Sussex was also Lord Chamberlain of the Queen’s Household and patron of the first Lord Chamberlain’s acting company. Two examples: (1) On New Year’s Day 1577 at Hampton Court the Paul’s Boys performed “The historie of Error,” which sounds like an early version of The Comedy of Errors attributed to Shakespeare; and (2) in Febrary 1577 at Whitehall Palace the Lord Chamberlain’s Men performed “The Historie of the Solitarie Knight,” which may have been a version of Shakespeare’s drama Timon of Athens.
When Edward de Vere was 30 in 1580 his secretary Lyly brought out his second book Euphues and His England, dedicated to Oxford and depicting an “Italianate” Englishman just like the earl himself. (The two books, which Oxford may have partially or wholly dictated, were virtually the first English novels.) Also in his service was Anthony Munday, whose Zelauto, the Fountain of Fame of 1580 was the second book he dedicated to Oxford; and in the same year Oxford also took complete charge of the Earl of Warwick’s adult acting company, whose leading men were the brothers Lawrence and John Dutton.
In addition to his patronage of writers, Lord Oxford now had charge of two acting companies, one consisting of adults (Oxford’s Men) and the other (Oxford’s Boys) consisting of choir boys from both Her Majesty’s Children of the Royal Chapel and Paul’s Boys. And he had the full sanction of the government; for example, his father-in-law William Cecil Lord Burghley, the Queen’s powerful chief minister, along with Lord Chamberlain Sussex, recommended to Cambridge University in mid-1580 that Oxford’s Men should be allowed to “show their cunning in several plays already practiced by them before the Queen’s Majesty.”
In 1583 Edward de Vere stepped forth to save the private Blackfriars Playhouse from extinction, by paying for the lease of this historic performance space. (It was frequented by aristocrats and students, with performances functioning as rehearsals for appearances in front of Queen Elizabeth at Court.) Soon afterward he passed on the lease to John Lyly, his director-manager. Oxford was now at the very center of the new awakening of English literature and drama in England that would lead to “Shakespeare” in the following decade.

Thomas Radcliffe, 3rd Earl of Sussex (1526-1583), Oxford's friend and surrogate father, whose Lord Chamberlain's Men brought plays to Court until his death
Oxford’s friend the Lord Chamberlain Sussex fell ill and was nearing death when the order came down on March 10,1583 to Edmund Tilney, Master of the Revels, that Her Majesty’s acting company be formed. In effect the Queen’s Men would take over from the Chamberlain’s Men. (Sussex died that June.) Assigned to assemble the personnel was secret service director Walsingham, who had no personal care for the theatre and had probably never set foot in a playhouse; but he was quite aware of the power of the drama.
As the Walsingham biography in Wikipedia observes, formation of the Queen’s Men “also signaled a new awareness on behalf of the Queen and the privy council of the potential for combining theatrical and espionage activities, since players frequently traveled, both nationally and internationally, and could serve the Crown in multiple ways, including the collection of information useful to Walsingham’s spy network.”
The spymaster assembled the Queen’s Men by first enlisting the twelve best performers from all the existing companies. These of course included Oxford’s Men, whose leading players the Dutton brothers as well as other actors were transferred into Her Majesty’s troupe. The popular clown Richard Tarlton was taken from Sussex’s troupe the Chamberlain’s Men and he quickly became the star of the Queen’s Men, which was now the largest company of actors in English Renaissance theatre.
“The new Queen’s Company made its first appearance at the beginning of the Court season on December 26, 1583,” B.M. Ward reported in The Seventeenth Earl of Oxford from Contemporary Documents (1928). “On January 1, 1584 a performance was given by Oxford’s Men; and as John Lyly appears in the Chamber Accounts as payee for the company on that date, there is every reason to believe, with Sir Edmund Chambers, that the play acted was Lyly’s Campaspe. On March 8, 1584 both Oxford’s and the Queen’s Men performed; once again Lyly was payee for Oxford’s Men, and Sir Edmund confidently conjectures that the play acted was Sapho and Phao.
“Now, it seems unreasonable to suppose that two plays were presented on this day; the most likely solution, therefore, would be that the two companies [i.e., Oxford’s and the Queen’s] were amalgamated and rehearsed by Lord Oxford’s private secretary John Lyly, the author of the play. No other adult companies besides these two appeared at Court during this season … The simplest solution is surely the one I have suggested, viz., that when the Queen’s Company absorbed some of Oxford’s leading actors Lyly was lent unofficially [starting in 1584] as stage manager and coach.”
So Edward de Vere Earl of Oxford was in position to respond to the Crown’s need for patriotic plays of English royal history; and, too, he was very much involved in the creation and operation of the Queen’s Men, whose actors would perform anonymous plays in the 1580’s that “Shakespeare” would later transform into masterpieces — another strong link in the chain of evidence that Oxford and “Shakespeare” were one and the same dramatist.