Slice kielbasa into about 50 slices. In a large nonstick pan, add kielbasa, onions, and red bell pepper. Cook until slightly browned, about 4 minutes. Drain any fat.
To cook in crockpot: Add kielbasa, onions, and red peppers to crockpot. Stir in remaining ingredients and mix well. Cover and cook in crockpot on high heat 3½ hours or low heat 7 hours, until cabbage is soft.
To cook on stovetop: In a nonstick pot, add Kielbasa, onions, and red bell peppers. Cook until slightly browned, about 4 minutes. Drain any fat. Stir in remaining ingredients and mix well. Bring to a boil, turn down to simmer, cover, and cook about 1 hour until cabbage is soft.
Serving suggestions: Ladle 1⅔ cups into each bowl. Or, toast 1 slice of whole wheat or multigrain bread for each serving. Line each bowl or plate with 1 slice of toast. Top each with 1⅓ cups stew.