In a bowl, combine your sliced peaches with the lemon, sugar and cinnamon. Set aside to let the peaches absorb the other ingredients.
In another bowl or food processor, combine your dry ingredients.
Melt your butter, and pour it into the dry mixture before combining again until a crumble is formed. Add more melted butter for larger chunks if desired.
Pour your peaches into a large baking dish, before generously sprinkling the crumble over the top.
Bake in the oven for 45 mins, or until bubbling and the crumble is golden.