Heat olive oil in a large skillet over medium high heat. Add ground beef and onion and cook until beef has browned, about 3-5 minutes, making sure to crumble the beef as it cooks; drain excess fat and remove from heat.
Stir in black beans, corn, salsa, green chiles, taco seasoning and enchilada sauce.
Lightly coat the inside of a 4-qt slow cooker with nonstick spray.
Spread half of the tater tots onto the bottom of the slow cooker; top with ground beef mixture and remaining tater tots. Cover and cook on low heat for 3-4 hours. Add cheese during the last 30 minutes of cooking time.
Serve immediately, garnished with cilantro, if desired.