Preheat oven to 350 degrees.
Mix oats, flour, 3/4 cup brown sugar, and butter together in a bowl until crumbly.
Mix apples, pears, 1 1/2 cups brown sugar, and cinnamon together in a separate bowl; spread into the bottom of a 13x9-inch glass pan. Sprinkle oat mixture on top of apple-pear mixture.
Bake in the preheated oven until the top is golden brown, about 40 minutes.
Recipe Source: Adapted from: Allrecipes.com