Preheat oven to 475F and line baking sheet with parchment paper. Cut croissants in half and place open side face up. Bake for 8-10 minutes or until golden. Set aside.

Cook bacon according to package. Set cooked bacon aside. Once cooled, chop into bite size pieces.

In a small sauce pan, heat olive oil. Add diced onion and diced pepper and cook until softened and onions are translucent, about 5-7 minutes. Set aside to cool.

In a large bowl, whisk eggs. Add in milk and whisk until well combined. Mix in 1 cup gruyere cheese, salt, pepper, and sage.

In a greased 9x13 dish, rip croissants into bite size pieces and scatter in bottom of dish. Scatter bacon evenly on top.

Add the cooled peppers and onions to the egg mixture and stir until combined, then pour egg mixture over croissant mixture, and press down croissants until they are covered by the egg mixture.

Cover with aluminum foil and let sit 8 hours or overnight.

When ready to bake, heat oven to 350F. Sprinkle remaining 1 cup cheese on top of casserole and bake for 45 minutes. Scatter top with green onions. Let cool 15 minutes before serving.