Stir oats, cocoa powder, and coconut together in a large bowl.
Whisk sugar, milk, and butter together in a nonstick pot; bring to a boil and cook, stirring constantly, until sugar is completely dissolved, about 2 minutes. Remove from heat and stir vanilla extract into butter mixture.
Stir oat mixture into butter mixture until well-combined. Drop mixture by the spoonful onto waxed paper and let sit until set, at least 15 minutes.
