Was Gandalf on Middle-earth in the Second Age?

Question

Amazon's Rings of Power shows someone who may be Gandalf operating in the second age. When does Gandalf first arrive to Middle-earth in Tolkien's writings?

Answer 1

Gandalf was sent as a Wizard in the third age, but there are indications in Tolkien's later writings that he may have been to Middle-earth before that.

There are three main sources in Tolkien's writings that suggest the third age was not Gandalf's first time in Middle-earth.

"Suggestions for key dates" (February-March 1959)

The first of these is a late timeline Tolkien wrote of The Great March that the elves took to reach Valinor early in the First Age. In this timeline Tolkien has Gandalf in Middle-earth helping the elves.

Oromë remains for 12 years, and then is summoned to return for the councils and war-preparations. Manwë has decided that the Quendi should come to Valinor, but on urgent advice of Varda, they are only to be invited, and are to be given free choice. The Valar send five Guardians (great spirits of the Maiar) – with Melian (the only woman, but the chief) these make six. The others were Tarindor (later Saruman), Olórin (Gandalf), Hrávandil (Radagast), Palacendo, and Haimenar. Tulkas goes back. Oromë remains in Cuiviénen for 3 more years.
_{The Nature of Middle-earth - Part 1, Chapter XIII - "Key Dates"}

And in an earlier draft of the above text:

Oromë and Tulkas are needed for the War. The Valar send the Five Guardians (Olórin etc.), with special power.
_{The Nature of Middle-earth - Part 1, Chapter XIII - "Key Dates"}

This is the first age, not the second age, but it shows that Tolkien was at least okay with Gandalf and the other wizards having been sent to Middle-earth prior to the time they get sent in the third age.

"The Elessar" (?End of 1959–?March 1960)

The second text is "The Elessar", a rough four page manuscript about the history of the elfstone that Galadriel gives to Aragorn. In this text we can see Gandalf (Olórin) interacting with Galadriel in

And on a time Olórin came to Galadriel, who dwelt now under the trees of Greenwood the Great; and they had long speech together. For the years of her exile began to lie heavy on the Lady of the Noldor, and she longed for news of her kin and for the blessed land of her birth, but was not permitted yet to forsake Middle-earth. And when Olórin had told her many tidings she sighed, and said: ‘I grieve in Middle-earth, for leaves fall and flowers fade; and my heart yearns, remembering trees and grass that do not die. I would have these in my home.’ Then Olórin said: ‘Would you then have the Elessar?’
And Galadriel said: ‘Where now is the Stone of Eärendil? And Enerdhil is gone who made it.’ ‘Who knows?’ said Olórin. ‘Surely,’ said Galadriel, ‘they have passed over Sea, as almost all fair things beside. And must Middle-earth then fade and perish for ever?’ ‘That is its fate,’ said Olórin. ‘Yet for a little while that might be amended, if the Elessar should return. For a little, until the Days of Men are come.’ ‘If – and yet how could that be,’ said Galadriel. ‘For surely the Valar are now removed and Middle-earth is far from their thought, and all who cling to it are under a shadow.’
‘It is not so,’ said Olórin. ‘Their eyes are not dimmed nor their hearts hardened. In token of which look upon this!’ And he held before her the Elessar, and she looked on it and wondered. And Olórin said: ‘This I bring to you from Yavanna. Use it as you may, and for a while you shall make the land of your dwelling the fairest place in Middle-earth. But it is not for you to possess. You shall hand it on when the time comes. For before you grow weary, and at last forsake Middle-earth one shall come who is to receive it, and his name shall be that of the stone: Elessar he shall be called.’

The reference to Galadriel living in Greenwood the Great is to the second age section of Appendix B in the first edition of The Lord of the Rings, which had read:

In the beginning of this age many of the High Elves still remained. The exiled Noldor dwelt in Lindon, but many of the Sindar passed eastward and established realms in the forests far away. The chief of these were Thranduil in the north of Greenwood the Great, and Celeborn in the south of the forest. But the wife of Celeborn was Noldorin: Galadriel, sister of Felagund of the House of Finrod.
_{The Lord of the Rings - Appendix B - "The Tale of Years" - "The Second Age"}

This conception was later edited out with the 1965 second edition of The Lord of the Rings, but it establishes the context for "The Elessar", showing that this conversation with Gandalf was in the Second Age.

"Glorfindel" (November 1972 - September 1973)

In the final year of Tolkien's life, in an essay discussing Glorfindel's reincarnation, Tolkien describes his relation to Gandalf, and mentions what Gandalf was doing in the Second Age.

[Glorfindel] then became again a living incarnate person, but was permitted to dwell in the Blessed Realm; for he had regained the primitive innocence and grace of the Eldar. For long years he remained in Valinor, in reunion with the Eldar who had not rebelled, and in the companionship of the Maiar. To these he had now become almost an equal, for though he was an incarnate (to whom a bodily form not made or chosen by himself was necessary) his spiritual power had been greatly enhanced by his self-sacrifice. At some time, probably early in his sojourn in Valinor, he became a follower, and a friend, of Olórin (Gandalf), who as is said in The Silmarillion had an especial love and concern for the Children of Eru. That Olórin, as was possible for one of the Maiar, had already visited Middle-earth and had become acquainted not only with the Sindarin Elves and others deeper in Middle-earth, but also with Men, is likely, but nothing has yet been said of this.
_{The Peoples of Middle-earth - Part 2, Chapter XIII, "Last Writings"}

To recap:

• A c.1959 timeline of the first age has Gandalf helping out in the Great March.
• A c.1960 narrative shows a conversation between Galadriel and Gandalf in the Second Age.
• A c.1972 essay mentions that it's very likely Gandalf had already been visiting Middle-earth for a while and getting acquainted with its inhabitants.