In a mixing bowl, stir together the oats, brown sugar, flour, cinnamon and salt.
Pour in the melted butter and rub together with your fingers until you have a lightly moist crumbly mixture.
Sprinkle over top of your pie or chopped fruit and bake as directed in the recipe. (see note)
If baking separately, spread in a layer on a parchment lined baking sheet and bake in the centre of a 350°F (175C/155C Fan) preheated oven for 15 minutes.
Notes
If topping a pie or other recipe with separate baking instructions, bake as directed taking care to check the crumble topping along the way. This should go golden, but if the recipe bakes at a high temperature or for a long period of time, the oat topping may catch. In these cases, you may want to add the topping mid-way through baking or cover with aluminium foil to protect it from burning.For recipes that are not baked or if you are adding separately, bake as directed for the crumble topping in step 4 above.