Slow cooker sausages with peppers and onions

2 large onions, sliced thin
2 red bell peppers, sliced thin
3 cloves garlic, sliced thin
1/2 teaspoon salt
1 tablespoon olive oil
2 packages (10 links) Harmon's italian sausages
1 jar bertolli marinara sauce

Place onions, peppers, garlic, salt, and oil in a large microwave safe bowl. Cover and microwave 8 minutes. Drain and add to slow cooker. Stir in sauce and add sausage links. Cook on low 4 hours. Slice sausages into half inch pieces and serve with crusty bread