In these four selected texts, dated aproximately between 1770 and 1783, we aim to show the evolution in the written Bizcayan Basque of Juan Antonio Mogel, one of the creators of the so-called literary Bizcayan Basque, before he reachead his well known and characteristical model in works like Peru Abarca or Confesino ona around 1800. In fact, the evolution is constant: in the beginning he wrote following Guipuzcoan -not Bizcayan- patterns, specially the Jesuit Sebastian Mendiburu, his main source, but shortly after he attempted to write in a more cultivated Bizcayan Basque in the catechism of 1783. Throughout all this first period he did not use at all some of the most characteristical and distinctive -from Anibarro's- graphical signs of his spelling system: doubled vowels and p (instead of f).