Preheat the oven to 325 degrees F (165 degrees C).
Heat oil in a large nonstick skillet over medium. Add sausage; cook, stirring to crumble, until browned and mostly cooked through, about 5 minutes. Add peppers and light green parts of scallions; cook, stirring occasionally, until sausage is no longer pink and vegetables are mostly tender, about 4 minutes. Remove from heat; set aside to cool slightly.
While sausage cools, whisk together eggs, half-and-half, hot sauce, salt, onion powder, garlic powder, and pepper in a large bowl.
Grease a 9x13-inch baking dish with cooking spray.
Layer 8 hash brown patties evenly on bottom of greased dish. Sprinkle evenly with 1 1/2 cups of the sausage mixture. Sprinkle 1 cup of Cheddar evenly over top, and layer with 5 slices of the pepper Jack. Repeat once more, ending with a final layer of hash browns. Pour custard over the top layer of hash browns and into the dish. Cover baking dish with foil.
Bake in the preheated oven, covered, until sides are mostly set, about 1 hour 20 minutes. Uncover and continue to bake until top layer of hash browns is golden brown and custard is set, about 40 minutes. Let stand 15 minutes before serving.
Sprinkle with dark green parts of scallion before serving. Recipe developed by Julia Levy