In a small saucepan, on medium-low heat, melt the butter. Add the garlic and cook for 1-2 minutes. Squeeze in the lemon juice. Turn the heat to low and let those flavors mesh until the oven is nice and hot. Season with salt and parsley. Then whisk in the olive oil. Remove from heat.
Arrange your crab legs in a 9x13 baking dish, brushing each leg with the sauce. Pour any remaining sauce over the top. Bake your crabs for about 25 minutes, brushing the sauce from the bottom of the pan onto the legs every 5-7 minutes.
Remove from oven. Sprinkle with a few pinches of parsley for garnish.