This is a easy dessert which can be prepared ahead and also freezes well.
Peel and slice pears.
Make the topping. I'm really bad at measuring and make this entirely by eye, however,I usually use about 1 oz butter/margarine per person.
Mix the fat with oats and flour until it has the consistency of gooey breadcrumbs. I think the secret of success is to be generous with the oats and mean with the flour. Use approximately twice the weight of oats/flour to that of fat. My preference is that at least half of the dry mixture is oats.
Add sugar to taste.