1. Brown sausage in a 10-inch (2-inch-deep) ovenproof nonstick skillet over medium-high heat, stirring often, 7 to 8 minutes or until meat crumbles and is no longer pink; remove from skillet, and drain. Wipe skillet clean.
2. Preheat oven to 350°. Heat oil in skillet over medium-high heat.
3. Add garlic, and sauté 1 minute. Stir in spinach, and cook, stirring constantly, 1 minute or just until spinach begins to wilt.
4. Add sausage, tomatoes and green chiles, salt, and pepper, and cook, stirring frequently, 2 to 3 minutes or until spinach is wilted. Add eggs, and sprinkle with cheese. Cook 3 to 5 minutes, gently lifting edges of frittata with a spatula and tilting pan so uncooked portion flows underneath.
5. Bake at 350° for 12 to 15 minutes or until set and lightly browned. Remove from oven, and let stand 5 minutes. Slide frittata onto a large platter, and cut into 8 wedges.
*1 (32-oz.) carton egg substitute may be substituted. Increase bake time to 16 to 18 minutes or until set.
**Plain feta cheese may be substituted.
Note: We tested with Ro-Tel Mild Diced Tomatoes and Green Chilies.