In a large skillet, heat oil over medium-high heat. Brown beef in batches; remove with a slotted spoon to a 4- or 5-qt. slow cooker. Add the pumpkin, potatoes, squash and onion. Stir in the broth, tomatoes and seasonings. Cover and cook on low for 6-8 hours or until meat is tender.
Remove bay leaves. In a small bowl, mix water and flour until smooth; gradually stir into stew. Cover and cook on high for 30 minutes or until liquid is thickened.