diff --git a/src/stpipe/pipeline.py b/src/stpipe/pipeline.py
index 70eaf00c..356b46bd 100644
--- a/src/stpipe/pipeline.py
+++ b/src/stpipe/pipeline.py
@@ -37,6 +37,7 @@ def __init__(self, *args, **kwargs):
         Step.__init__(self, *args, **kwargs)
 
         # Configure all of the steps
+        step_parameters = kwargs.get('steps', {})
         for key, val in self.step_defs.items():
             cfg = self.steps.get(key)
             if cfg is not None:
@@ -44,7 +45,7 @@ def __init__(self, *args, **kwargs):
                     cfg,
                     parent=self,
                     name=key,
-                    config_file=self.config_file,
+                    config_file=self.config_file
                 )
             else:
                 new_step = val(
@@ -54,6 +55,13 @@ def __init__(self, *args, **kwargs):
                     **kwargs.get(key, {}),
                 )
 
+            # Make sure explicitly passed parameters for sub-steps
+            # are marked as initialized
+            input_parameters = step_parameters.get(key, {})
+            for param in input_parameters:
+                if param in new_step._initialized:
+                    new_step._initialized[param] = True
+
             setattr(self, key, new_step)
 
     @property
diff --git a/src/stpipe/step.py b/src/stpipe/step.py
index 6a697ffd..b6ef2fa1 100644
--- a/src/stpipe/step.py
+++ b/src/stpipe/step.py
@@ -364,8 +364,10 @@ def __init__(
         for key, val in kws.items():
             setattr(self, key, val)
 
-            # Mark them as uninitialized, from the user standpoint
-            self._initialized[key] = False
+            # Mark them as uninitialized, from the user standpoint,
+            # unless they were explicitly passed on instantiation
+            if key not in self._keywords or parent is not None:
+                self._initialized[key] = False
 
         # Create a new logger for this step
         self.log = log.getLogger(self.qualified_name)
@@ -439,8 +441,10 @@ def run(self, *args, **kwargs):
         The order of parameter checking and overrides is:
            1. spec default value for the step
            2. keyword parameters or configuration set on step initialization
-           3. CRDS parameters if available
-           4. step attributes directly set by the user before calling run
+           3. CRDS parameters if available and if CRDS checks are not disabled
+           4. step attributes explicitly set by the user before calling run,
+              either on instantiation or by directly setting the attribute
+              after instantiation.
            5. keyword parameters passed directly to the run call
 
         Only 1 and 2 are checked if the step was created via `call`
@@ -460,6 +464,9 @@ def run(self, *args, **kwargs):
 
             self.log.info("Step %s running with args %s.", self.name, args)
 
+            # Check for explicit disable for CRDS parameters
+            disable_crds_steppars = kwargs.pop('disable_crds_steppars', None)
+
             # Get parameters from user
             parameters = None
             if kwargs:
@@ -478,7 +485,8 @@ def run(self, *args, **kwargs):
 
                 # Build config from CRDS + user keywords
                 try:
-                    parameters, _ = self.build_config(filename, **kwargs)
+                    parameters, _ = self.build_config(
+                        filename, disable=disable_crds_steppars, **kwargs)
                 except (NotImplementedError, FileNotFoundError):
                     # Catch steps that cannot build a config
                     # (e.g. post hooks created from local functions,
@@ -1381,7 +1389,7 @@ def update_pars(self, parameters, skip_initialized=False):
                 )
 
     @classmethod
-    def build_config(cls, input, **kwargs):  # noqa: A002
+    def build_config(cls, input, disable=None, **kwargs):  # noqa: A002
         """Build the ConfigObj to initialize a Step
 
         A Step config is built in the following order:
@@ -1395,6 +1403,9 @@ def build_config(cls, input, **kwargs):  # noqa: A002
         input : str or None
             Input file
 
+        disable : bool, optional
+            Do not retrieve parameters from CRDS. If None, check global settings.
+
         kwargs : dict
             Keyword arguments that specify Step parameters.
 
@@ -1406,7 +1417,7 @@ def build_config(cls, input, **kwargs):  # noqa: A002
         logger_name = cls.__name__
         log_cls = log.getLogger(logger_name)
         if input:
-            config = cls.get_config_from_reference(input)
+            config = cls.get_config_from_reference(input, disable=disable)
         else:
             log_cls.info("No filename given, cannot retrieve config from CRDS")
             config = config_parser.ConfigObj()
diff --git a/tests/test_step.py b/tests/test_step.py
index 4cbe8245..3b541b02 100644
--- a/tests/test_step.py
+++ b/tests/test_step.py
@@ -462,6 +462,38 @@ def test_step_run_crds_values(step_class):
     assert step._initialized["str1"] is True
 
 
+@pytest.mark.usefixtures("_mock_crds_reffile")
+@pytest.mark.parametrize("step_class", [SimplePipe, SimpleStep])
+def test_step_run_disable_crds_explicit(step_class):
+    """Test that CRDS parameters are not checked if disabled."""
+    step = step_class()
+    step.process = lambda *args: None
+
+    assert step.str1 == "default"
+    assert step._initialized["str1"] is False
+
+    step.run("science.fits", disable_crds_steppars=True)
+    assert step.str1 == "default"
+    assert step._initialized["str1"] is False
+
+
+@pytest.mark.usefixtures("_mock_crds_reffile")
+@pytest.mark.parametrize("step_class", [SimplePipe, SimpleStep])
+def test_step_run_disable_crds_via_environment(monkeypatch, step_class):
+    """Test that CRDS parameters are not checked if disabled."""
+    step = step_class()
+    step.process = lambda *args: None
+
+    assert step.str1 == "default"
+    assert step._initialized["str1"] is False
+
+    monkeypatch.setenv('STPIPE_DISABLE_CRDS_STEPPARS', 'True')
+
+    step.run("science.fits")
+    assert step.str1 == "default"
+    assert step._initialized["str1"] is False
+
+
 @pytest.mark.usefixtures("_mock_crds_reffile")
 @pytest.mark.parametrize("step_class", [SimplePipe, SimpleStep])
 def test_step_run_initialized_values(step_class):
@@ -480,6 +512,21 @@ def test_step_run_initialized_values(step_class):
     assert step._initialized["str1"] is True
 
 
+@pytest.mark.usefixtures("_mock_crds_reffile")
+@pytest.mark.parametrize("step_class", [SimplePipe, SimpleStep])
+def test_step_run_initialized_values_on_instantiation(step_class):
+    """Test that parameters pre-set are not overridden when run is called."""
+    step = step_class(str1='on instantiation')
+    step.process = lambda *args: None
+
+    assert step.str1 == "on instantiation"
+    assert step._initialized["str1"] is True
+
+    step.run("science.fits")
+    assert step.str1 == "on instantiation"
+    assert step._initialized["str1"] is True
+
+
 @pytest.mark.usefixtures("_mock_crds_reffile")
 @pytest.mark.parametrize("step_class", [SimplePipe, SimpleStep])
 def test_step_run_keyword_values(step_class):
@@ -576,8 +623,8 @@ def test_pipe_run_step_values_skip_initialized():
     pipe = SimplePipe()
     pipe.process = lambda *args: None
 
-    # Step parameters are initialized when created via the pipeline
-    # from defaults
+    # Step parameters are not initialized when created via the
+    # pipeline from defaults
     assert pipe.step1.str1 == "default"
     assert pipe.step1._initialized["str1"] is False
 
@@ -588,3 +635,18 @@ def test_pipe_run_step_values_skip_initialized():
     pipe.run("science.fits")
     assert pipe.step1.str1 == "from user"
     assert pipe.step1._initialized["str1"] is True
+
+
+@pytest.mark.usefixtures("_mock_crds_reffile")
+def test_pipe_run_step_values_skip_initialized():
+    """Test that initialized parameters are not overridden."""
+    pipe = SimplePipe(steps={'step1': {'str1': 'on instantiation'}})
+    pipe.process = lambda *args: None
+
+    assert pipe.step1.str1 == "on instantiation"
+    assert pipe.step1._initialized["str1"] is True
+
+    # Parameters are not overridden by CRDS
+    pipe.run("science.fits")
+    assert pipe.step1.str1 == "on instantiation"
+    assert pipe.step1._initialized["str1"] is True