– 1 cup (125 grams) all-purpose flour , spooned & leveled – 1 1/4 cups (125 grams) old-fashioned rolled oat – 1/2 teaspoon baking soda – 1/4 teaspoon salt – 1/2 cup (115 grams) unsalted butter , softened – 3/4 cup (150 grams) brown sugar , lightly packed – 1/4 cup (50 grams) granulated sugar – 1/2 cup (125 grams) creamy peanut butter – 1 large egg , room temperature – 1 teaspoon pure vanilla extract – 3/4 cup (150 grams) M&M' – 1/2 cup (95 grams) semi-sweet chocolate chip