Spray 13x9-inch (3-quart) glass baking dish or 3-quart oval casserole with cooking spray. Spread 1/3 of the bread cubes in baking dish. Top evenly with 1/3 of the bell pepper and onion stir-fry and 1/3 of the beef. Sprinkle with 1/3 of the cheese. Repeat layers twice, ending with cheese.
In large bowl, beat eggs. Stir in all remaining ingredients; pour evenly over cheese. Cover tightly with foil; refrigerate at least 8 hours or overnight.
When ready to bake, heat oven to 350°F. Uncover baking dish; bake 40 to 50 minutes or until puffed, top is golden brown and center is set. Let stand 10 minutes before serving.