Preheat the oven to 350 degrees F. Grease a 9x13 baking dish and set aside.
Combine the trimmed green beans and thinly sliced onion in a large mixing bowl. In a separate bowl, whisk together the ketchup, Worcestershire sauce, maple syrup, and garlic powder. Pour over the green beans and onions. Mix until well coated.
Transfer to the baking sheet, and bake for ~20-25 minutes, or until the green beans and onions are tender. Enjoy!
You can prep these in advance and keep in a covered baking dish in the fridge until you are ready to cook them.