Layer cooked chorizo, pepper jack cheese and green onions in prepared 24 x 16 x 1-inch pan; set aside.
Place Krusteaz Professional Buttermilk Pancake Mix, milk and eggs in mixer bowl.
Using a paddle, mix on low speed 30 seconds. Scrape bowl and paddle. Continue to mix on low speed 1 minute.
Pour batter over ingredients in pan.
For convection oven, bake at 300°F 15-18 minutes; for standard oven, bake at 350°F 20-25 minutes. Casserole is done when knife inserted into center comes out clean.