Preheat an oven to 350 degrees F (175 degrees C). Arrange the graham crackers in a single layer on a baking sheet, making sure the crackers touch each other.
Heat the butter, margarine, and white sugar in a saucepan over medium heat until the sugar is dissolved, about 2 minutes. Stir in the pecans.
Spread the butter mixture over the graham crackers.
Bake in the preheated oven until butter mixture is absorbed, 8 to 10 minutes. Immediately transfer the crackers to cool on aluminum foil or wax paper. Once cooked, break crackers into bite-sized pieces.
