Preheat the oven to 375 degrees F (190 degrees C). Arrange bacon slices on a slotted baking pan.
Bake bacon in the preheated oven until partially cooked but still flexible, 6 to 8 minutes.
Brush venison tenderloins with olive oil and season with onion powder, salt, and black pepper. Place tenderloin roasts side by side and wrap them together in strips of partially cooked bacon. Place into a roasting pan.
Roast in the preheated oven until bacon is browned and an instant-read meat thermometer inserted into the thickest part of a tenderloin reads at least 145 degrees F (65 degrees C), about 1 hour.
Heat butter in a saucepan over medium heat. Add mushrooms and garlic; cook and stir until mushrooms are soft, 8 to 10 minutes. Stir in green onion. Stir in cream and cook, stirring often, until heated through. Serve sauce with tenderloins.