Preheat your oven to 400 degrees F and grease the inside of a 9x13 baking dish. Set it aside.
Wash your red potatoes (peeling is optional) and dice into 1 inch sized cubes.
Place the potatoes into a large mixing bowl and add in the seasonings. Set aside.
Slice your smoked sausage into ¼ inch sliced coins and place them into a skillet over medium-high heat. Cook until browned on both sides.
Add your sausage to the bowl of potatoes.
Add the butter to the skillet and cook your onions and garlic for about 3 minutes or until the onions are soft.
Add the onions to the mixing bowl.
Gently mix everything in the bowl together until well combined.
Lightly mix in the green beans, being careful so that they don't break.
Pour the mixture into the prepared baking dish.
Cover the top of the dish well with aluminum foil.
Bake in the oven for 40-45 minutes or until the potatoes are fork-tender.