Preheat your oven to 375 degrees F (190 degrees C).
Place Gala Apples (6) in a large bowl. Add Granulated Sugar (1/2 cup), Ground Cinnamon (1 teaspoon), Vanilla Extract (1 teaspoon), if using, and All-Purpose Flour (1 tablespoon). Mix all together.
In a separate bowl, mix Old Fashioned Rolled Oats (1 cup), All-Purpose Flour (1 cup), Ground Cinnamon (1 teaspoon), Salt (1/4 teaspoon) and Brown Sugar (3/4 cup) for the crumbly topping then rub in the Butter (12 tablespoon) until clumps form, it will look like wet sand.
Spread apples evenly on a baking dish (8x8 or 13x9-inch will both work). Spread topping over the apples.
Transfer baking dish to a baking sheet to avoid mess in the oven. Then bake for 40-45 minutes or until golden brown.
Allow to cool for 10 minutes before serving. Serve with vanilla ice cream.