Cook grits in a small saucepan according to package directions, omitting salt and fat. Add cheese, stirring until cheese melts. Cover and keep warm.
Coat a small nonstick skillet with cooking spray; place over medium heat until hot. Add mushrooms; saute 2 minutes. Add garlic; saute 1 minute. Remove from heat. Stir in beef broth and remaining ingredients.
Add mushroom mixture to grits, stirring well. Serve immediately.