Pre-heat oven to 400° F.

In a small bowl, mix together the onion, sage, salt, and pepper.

Fill the mushroom caps with the onion mixture. Place the filled mushroom caps in a heat-proof dish.

Set the 1/4 slice of bacon on top of the filled mushroom and wrap it around the sides. Secure the bacon ends with a toothpick and place the mushroom cap back in the dish. Repeat until all mushrooms are wrapped.

Bake the mushrooms in the preheated oven for 40 minutes or until the bacon has crisped on top and the mushrooms are browned and juicy.

Line a dinner plate with papertowels. Carefully remove the mushrooms from the hot dish and set them on the papertowel to drain for 1-2 minutes.

Arrange mushrooms on serving dish and serve warm.