Preheat oven to 400°F. Grease a 13-by-9-inch baking dish with butter. Whisk eggs, milk, syrup, vanilla, nutmeg, and 2 tablespoons melted butter in a large bowl. Add oats, baking powder, and salt; stir to combine. Transfer to baking dish; spread in a mostly even layer using a spatula. Top with berries and almonds.
Bake until lightly golden and firm in center, 40 to 45 minutes. Let rest for 10 minutes. Drizzle or brush with remaining 2 tablespoons melted butter. Serve with more syrup.
