As it is on the Dollar Menu, it is offered for $1.
The burger reminds me a smaller version of the recent Cheddar Bacon Onion, but somehow the one I ordered contained more onions than the "premium" Cheddar Bacon Onion that I tried. The onions were grilled to the point of charring and delivered a strong, slightly sweet flavor uninhibited by any sauces or other powerful flavors. I worry that the amount of onions given will vary wildly from location to location marring what should be a consistent experience.
The bun had a nice squishiness and wasn't too dense or light. McDonald's regular hamburger bun is actually very nice.
Nutritional Info - McDonald's Grilled Onion Cheddar Burger (115g)
Calories - 310 (from Fat - 120)
Fat - 13g (Saturated Fat - 6g)
Sodium - 660mg
Carbs - 33g (Sugar - 7g)
Protein - 15g