Cut potatoes into bite-size pieces and place in a bowl. Toss with olive oil. In a small bowl, stir together melted butter, garlic powder, salt, and pepper. Drizzle over potatoes and toss evenly.
Line a baking sheet with a Silpat, parchment paper, or aluminum foil spray with non-stick cooking spray. Pour potato mixture onto the pan.
Bake for 30-40 minutes, depending on the size of the potatoes. Flip the potatoes halfway through cooking time. Watch carefully and pierce with a fork to know if the potatoes are completely cooked through.
Toss with fresh parsley and more garlic butter, if so desired.