Preheat oven to 300 degrees. In 9" pie plate, with hand, mix coconut, oats, and 3 tablespoons softened butter. Pat mixture into bottom and up side of pie plate. Bake crust 15 minutes or until golden. Cool on wire rack.
In 2 quart saucepan, mix milk, cornstarch, egg yolks, 1/2 cup sugar, 2 tablespoons butter and 1/4 teaspoon salt until well mixed. Cook over medium low heat, stirring constantly, until mixture boils and thickens; boil 1 minute. Remove saucepan from heat; stir in vanilla.
Slice 2 bananas 1/4" thick. Line cooled pie shell with sliced bananas; pour custard filling over bananas. Top with meringue.