Preheat oven to 425°.
Trim fat from venison; place venison on a rack coated with cooking spray. Sprinkle with 1/2 teaspoon salt and 1/8 teaspoon pepper; insert a meat thermometer into the thickest part of venison. Bake at 425° for 30 minutes or until thermometer reaches 145° (medium-rare) to 160° (medium). Cover loosely with foil; let stand 10 minutes.
Remove stems from mushrooms and discard; slice caps. Place a large nonstick skillet coated with cooking spray over medium-high heat until hot. Add mushrooms and shallots; sauté 4 minutes or until tender. Add 1/4 teaspoon salt, 1/8 teaspoon pepper, and port; cook 2 minutes. Combine broth and cornstarch in a small bowl. Add to skillet; bring to a boil, and cook 1 minute or until thick, stirring constantly. Serve with venison.
Note: Beef tenderloin can be substituted for venison.