diff --git a/click/_bashcomplete.py b/click/_bashcomplete.py
index d9d26d28b..9d60fa2bb 100644
--- a/click/_bashcomplete.py
+++ b/click/_bashcomplete.py
@@ -40,18 +40,30 @@ def resolve_ctx(cli, prog_name, args):
 
 
 def get_choices(cli, prog_name, args, incomplete):
+    # resolve_ctx will change args in place
+    # need to grab the last completed one here and now
+    last_complete = [a for a in (args if args else ['']) if a != '='][-1]
+    if incomplete == '=':
+        incomplete = ''
+
     ctx = resolve_ctx(cli, prog_name, args)
     if ctx is None:
         return
 
     choices = []
+
+    if last_complete:
+        for param in ctx.command.params:
+            if last_complete in param.opts:
+                choices.extend(param.get_completion())
+                break
     if incomplete and not incomplete[:1].isalnum():
         for param in ctx.command.params:
             if not isinstance(param, Option):
                 continue
             choices.extend(param.opts)
             choices.extend(param.secondary_opts)
-    elif isinstance(ctx.command, MultiCommand):
+    if isinstance(ctx.command, MultiCommand):
         choices.extend(ctx.command.list_commands(ctx))
 
     for item in choices:
diff --git a/click/core.py b/click/core.py
index cb43d537f..b87fa31de 100644
--- a/click/core.py
+++ b/click/core.py
@@ -1260,7 +1260,8 @@ class Parameter(object):
 
     def __init__(self, param_decls=None, type=None, required=False,
                  default=None, callback=None, nargs=None, metavar=None,
-                 expose_value=True, is_eager=False, envvar=None):
+                 expose_value=True, is_eager=False, envvar=None,
+                 completer=None, choices=None):
         self.name, self.opts, self.secondary_opts = \
             self._parse_decls(param_decls or (), expose_value)
 
@@ -1283,6 +1284,8 @@ def __init__(self, param_decls=None, type=None, required=False,
         self.is_eager = is_eager
         self.metavar = metavar
         self.envvar = envvar
+        self.completer = completer
+        self.choices = choices
 
     @property
     def human_readable_name(self):
@@ -1415,6 +1418,15 @@ def get_help_record(self, ctx):
     def get_usage_pieces(self, ctx):
         return []
 
+    def get_completion(self):
+        if self.completer:
+            for thing in self.completer():
+                yield str(thing)
+        if self.choices:
+            for thing in self.choices:
+                yield str(thing)
+
+
 
 class Option(Parameter):
     """Options are usually optional values on the command line and
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/test_bashcomplete.py b/tests/test_bashcomplete.py
index fea096c10..01ca084ef 100644
--- a/tests/test_bashcomplete.py
+++ b/tests/test_bashcomplete.py
@@ -60,3 +60,31 @@ def csub(csub_opt):
     assert list(get_choices(cli, 'lol', ['asub', 'bsub'], '')) == ['csub']
     assert list(get_choices(cli, 'lol', ['asub', 'bsub', 'csub'], '-')) == ['--csub-opt']
     assert list(get_choices(cli, 'lol', ['asub', 'bsub', 'csub'], '')) == []
+
+
+def test_completer():
+
+    def custom_completer():
+        yield 'custom'
+        for i in [0, 1, 2]:
+            yield i
+        yield 'bye'
+
+    @click.command()
+    @click.option('--local-opt', completer=custom_completer)
+    def cli(local_opt):
+        pass
+
+    assert list(get_choices(cli, 'lol', [], '-')) == ['--local-opt']
+    assert list(get_choices(cli, 'lol', ['--local-opt'], '')) == ['custom', '0', '1', '2', 'bye']
+
+
+def test_choices():
+
+    @click.command()
+    @click.option('--local-opt', choices=['foo', 'bar', 'spam', 'eggs'])
+    def cli(local_opt):
+        pass
+
+    assert list(get_choices(cli, 'lol', [], '-')) == ['--local-opt']
+    assert list(get_choices(cli, 'lol', ['--local-opt'], '')) == ['foo', 'bar', 'spam', 'eggs']