Preheat the oven to 350°F. Spray a 9x13-inch (or deep 8x8-inch) baking pan with nonstick spray. Set aside.
Whisk the pumpkin puree, half-and-half, stevia, eggs, 2 teaspoons pumpkin pie spice, and ½ teaspoon salt together in a large bowl until well blended. Set aside.
30 ounces pumpkin puree, 2 cups half-and-half, 1½ cups Stevia in the Raw (Baker's Bag), 3 large eggs, 2½ teaspoons pumpkin pie spice, ½ teaspoon kosher salt
In another large bowl, combine the oats, pecans, brown sugar (if using), flour, and remaining ½ teaspoon pumpkin pie spice, breaking up any lumps of brown sugar with a fork. Melt the butter and stir into the flour mixture until it is completely combined.
1 cup old-fashioned rolled oats, ½ cup roasted pecans, ½ cup dark brown sugar, ¾ cup all-purpose flour, 8 tablespoons salted butter
Spread the pumpkin mixture evenly in the bottom of the baking dish. Pinch the oat mixture onto the top. Bake until golden and fully cooked, about 50 minutes.
Serve warm with ice cream or whipped cream, if desired.
Ice cream, Homemade whipped cream