Place the potatoes on your clean cutting board. Slice them into half-inch thick rounds or wedges. Try to keep the sizes very even for cooking.

Put the potato slices into your large mixing bowl. Pour the olive oil over the top of them. Toss them well until every piece is shiny.

Sprinkle the salt and garlic powder over the bowl. Add the black pepper and the dried rosemary now. Toss again so the spices coat every single slice.

Preheat your outdoor grill to a medium-high heat setting. Clean the grates so the potatoes do not stick. Lightly oil the grates using a brush or cloth.

Place the potato slices directly onto the hot grill. Close the lid to trap the heat inside well. Let them cook for about five minutes per side.

Use your tongs to flip each potato slice carefully. Look for dark grill marks on the bottom side. Cook the other side for five more minutes.

Check the softness with a fork or a toothpick. Remove them from the grill once they are tender. Garnish with fresh parsley before you serve them hot.