Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish or casserole dish

Cook the sausage and veggies: In a skillet over medium heat, cook the breakfast sausage until browned and fully cooked. Remove with a slotted spoon, leaving some of the fat in the pan. Add the diced bell peppers and onion, sautéing until softened (about 3-4 minutes). Remove from heat.

Assemble the bake: Spread the quartered biscuits evenly in the greased baking dish. Top with the cooked sausage, sautéed veggies, and 1 ½ cups of shredded Gruyère cheese.

Make the custard: In a medium bowl, whisk together the eggs, half and half, salt, and pepper. Pour the mixture evenly over the biscuit mixture, pressing down slightly to help the biscuits absorb the custard.

Let it rest (optional, but recommended): Allow the casserole to sit for about half an hour, up to overnight, before baking to ensure the biscuits soak up the egg mixture.

Bake for 35-40 minutes, or until the eggs are set and the top is golden brown. Sprinkle with the remaining ½ cup of Gruyère in the last 5 minutes of baking for extra melty goodness.

Serve & enjoy: Let the bake cool for a few minutes before slicing. Serve warm and enjoy!