Preheat the oven to 350 degrees F (175 degrees C). Butter an 8-inch baking or casserole dish.

Heat a large skillet over medium-high heat. Cook and stir ground beef and onion in the hot skillet until beef is browned and crumbly, 5 to 7 minutes. Mix in corn, tomatoes, oil, chili powder, and cumin. Bring to a boil; remove from heat.

Combine milk, cornmeal, and eggs in a large bowl. Stir in meat mixture. Mix in olives. Pour into the prepared baking dish.

Bake in the preheated oven until golden and set, 50 to 60 minutes; mixture should not be mushy.