Preheat oven to 375 degrees F. Mix olive oil, chili powder, cumin, garlic powder, salt, and pepper in a medium bowl. Add chicken and stir to coat.
Heat skillet over medium-high heat and spray with cooking spray (I like my 10″ iron skillet best). Cook chicken approximately 7 minutes per side, until brown and cooked through. Remove to cutting board and let rest a few minutes.
While chicken is resting, arrange tostadas in a single layer on two baking sheets. Spread each tostada evenly with refried beans.
Slice chicken into thin strips, and arrange on top tostadas. Sprinkle each tostada with 2 tbsp. shredded cheese.
Bake in preheated oven for 8-10 minutes, until cheese is melted. Serve with desired toppings and enjoy.