Preheat oven to 350°F. Lightly grease or spray with nonstick cooking spray an 8-inch square baking dish.
Spread chopped pecans on an ungreased baking sheet and toast for 4 to 6 minutes or until fragrant and light golden brown. Cool on baking sheet.
In a large bowl, mix together mashed banana, milk, eggs, coconut oil, maple syrup, and vanilla; beat until smooth. Blend in oats, ½ cup toasted pecans, cinnamon, and salt; stir until mixture is well-combined.
Spread oatmeal into prepared baking dish and bake for 20 to 25 minutes or until set and light golden brown on top. Allow to cool in the baking dish for at least 5 minutes before slicing. Serve warm with optional garnishes: warm milk or cream drizzled over the top, additional toasted pecans, maple syrup, or fresh fruit.
