Preheat oven to 425 degrees F (220 degrees C).

Combine potatoes, oil, Mexican seasoning, and garlic salt together in a bowl; stir to coat potatoes completely. Spread potatoes in a single layer on a baking sheet.

Bake in the preheated oven, stirring occasionally, until potatoes are crisp and golden brown, 25 to 30 minutes.

Transfer potatoes to a plate and top with Mexican cheese blend, black beans, diced tomatoes, black olives, green onions, and green chiles.