Place the beef stew meat in the slow cooker.
In a bowl, whisk together the peanut butter, soy sauce, coconut milk, brown sugar, lime juice, garlic, and ginger until smooth.
Pour the sauce over the beef and add the sliced red bell pepper.
Cover and cook on low for 6 to 7 hours until the beef is tender.
Stir the cooked rice noodles into the beef and sauce right before serving.
Top each bowl with chopped peanuts and sliced green onions.