Set a large sauté pan over high heat, add beef, onions and garlic. Sauté for 4-5 min. until lightly browned. Season with garlic powder, onion powder and dried oregano. Cook for 7-8 min. until well browned. Add tomato paste and Worcestershire sauce; stir well. Cook 5 min. more until cooked through. Add crushed RITZ Crackers to tighten up the mixture. Keep warm.
Heat broiler. Cut rounds out of cheese slices using a 2-inch round biscuit or cookie cutter. (You should get 2 rounds from each cheese slice; reserve scraps for other use.) Top each RITZ Cracker with 1 teaspoon of lightly packed beef mixture. Place a piece of jalapeno on each then top with a round of cheese. Set out on a roasting tray and broil for 1-2 min. until cheese has melted and is bubbly.