Heat oven to 350°. Grease an 8-by-8-inch baking pan and set aside.
Combine oats, brown sugar, baking powder, cinnamon, and salt in a large bowl. In a separate bowl, whisk together half and half, egg, butter, and vanilla. Pour wet ingredients over dry ingredients and stir until thoroughly combined. Gently fold in 1 cup of sliced strawberries. Pour oat mixture into prepared baking dish and sprinkle remaining strawberries over top.
Bake until golden brown and oat mixture has set, about 40 minutes. Remove from oven and let cool 5 minutes. Serve warm.