diff --git a/pyomo/core/base/indexed_component.py b/pyomo/core/base/indexed_component.py
index f38a968e714..0803e8e7c0b 100644
--- a/pyomo/core/base/indexed_component.py
+++ b/pyomo/core/base/indexed_component.py
@@ -360,15 +360,17 @@ def iteritems(self):
 
     def keys(self):
         """Return an iterator of the keys in the dictionary"""
-        return [ x for x in self ]
+        return iter(self)
 
     def values(self):
         """Return an iterator of the component data objects in the dictionary"""
-        return [ self[x] for x in self ]
+        for s in self:
+            yield self[s]
 
     def items(self):
         """Return an iterator of (index,data) tuples from the dictionary"""
-        return [ (x, self[x]) for x in self ]
+        for s in self:
+            yield s, self[s]
 
     def __getitem__(self, index):
         """
diff --git a/pyomo/core/tests/unit/test_compare.py b/pyomo/core/tests/unit/test_compare.py
index fe90f5f09cb..20131e4d17d 100644
--- a/pyomo/core/tests/unit/test_compare.py
+++ b/pyomo/core/tests/unit/test_compare.py
@@ -28,7 +28,7 @@ class TestConvertToPrefixNotation(unittest.TestCase):
     def test_linear_expression(self):
         m = pe.ConcreteModel()
         m.x = pe.Var([1, 2, 3, 4])
-        e = LinearExpression(constant=3, linear_coefs=m.x.keys(), linear_vars=m.x.values())
+        e = LinearExpression(constant=3, linear_coefs=list(m.x.keys()), linear_vars=list(m.x.values()))
         expected = [(LinearExpression, 9), 3, 1, 2, 3, 4, m.x[1], m.x[2], m.x[3], m.x[4]]
         pn = convert_expression_to_prefix_notation(e)
         self.assertEqual(pn, expected)