Preheat an oven to 325°F. Line 2 baking sheets with parchment paper.

In a bowl, thoroughly stir together the flour, baking soda, and salt, then stir in the oats and coconut. In a large bowl, cream the brown sugar and butter with a wooden spoon until fluffy. Stir in the banana, egg and vanilla. Stir in the flour mixture, about ½ cup at a time, then stir in the chocolate and nuts.

Spoon the dough by heaping tablespoonfuls onto the prepared baking sheet(s), spacing the cookies about 2 inches apart. Bake one sheet at a time until golden brown, 12 to 15 minutes.

Remove from the oven and let the cookies cool on the baking sheet(s) on a wire rack for about 5 minutes. Transfer the cookies to the rack and let cool completely. Store in an airtight container at room temperature for up to 3 days.