Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.

Place bacon, onion, bell peppers, salt, and pepper into a large skillet and cook over medium-high heat, turning occasionally, until bacon is evenly browned and crispy, about 10 minutes. Add ground beef and cook until browned and crumbly, 5 to 7 minutes. Mix in mushroom soup and milk. Transfer mixture to the prepared baking dish.

Top casserole with Tater Tots®, followed by Cheddar cheese.

Bake in the preheated oven until Tater Tots® are golden and heated though and cheese is bubbly, 30 to 35 minutes.