To say that the mass was ever a conventional “meal” would be rather inaccurate, especially in light of St. Paul’s words regarding gluttony and drunkeness at mass. I will agree though, that it was far more “meal-like” in the early years.
However, the document by Justin Martyr, which I believe is from the year 160 AD, shows some real similarities to the Tridentine mass. As I recall, it contains descriptions of parts of the mass such as the Kiss of Peace, and the Consecration. The Institute of Christ the King Soverign Priest has a blurb about the development of the mass on their website, explaining how from the time we see the first missals c. 600 AD up until 1500 AD, when the mass was standardized, changes were very few, and of an evolutionary nature. The changes since then, they say, have been similarly slow, minimal, and mostly pragmatic.
I like to think that, as someone familiar with the Tridentine mass, if I were to, hypothetically, travel back in time and hear St. Augustine say mass, I would be capable of at least following along.