Grease a large sheet pan with 1 tablespoon oil. Place the green beans on the baking sheet in a single layer. Drizzle remaining oil over the green beans and toss to coat. Sprinkle the taco seasoning evenly over the green beans.
Bake on the center rack of oven for 30 minutes, Turning once during baking.Start checking for done at 20 minutes. Remove from the oven when beans have just started to develop dark charred spots.