1. Place a large skillet over medium high heat and add the oil. Once the oil is heated, add the onions, and allow to brown, about 5 minutes.
  2. Spread the onions to the outer edge of the pan and add in the hot dogs. Turn occasionally and allow to brown for 3-5 minutes.
  3. Once the hotdogs are brown, pour the beer into the pan, turn burner to low and allow to simmer for 15 minutes.
  4. Remove pan from heat and place hot dogs in buns. Top with cooked onions and spicy brown mustard. Serve.