diff --git a/taskcluster/ci/test/compiled.yml b/taskcluster/ci/test/compiled.yml
index 263f4e505ff2..87d8c03309e4 100644
--- a/taskcluster/ci/test/compiled.yml
+++ b/taskcluster/ci/test/compiled.yml
@@ -4,7 +4,7 @@
 ---
 job-defaults:
     test-manifest-loader: null  # don't load tests in the taskgraph
-    e10s:
+    run-without-variant:
         by-test-platform:
             android.*: true
             default: false
diff --git a/taskcluster/ci/test/mochitest.yml b/taskcluster/ci/test/mochitest.yml
index 0ba379142bc6..ca92b197f61d 100644
--- a/taskcluster/ci/test/mochitest.yml
+++ b/taskcluster/ci/test/mochitest.yml
@@ -128,7 +128,7 @@ mochitest-a11y:
     schedules-component: mochitest-a11y
     test-manifest-loader: default  # ensure we don't run with manifest-scheduling
     loopback-video: true
-    e10s: false
+    run-without-variant: false
     variants:
         - 1proc
         - socketprocess_networking+1proc
@@ -338,7 +338,7 @@ mochitest-chrome:
     treeherder-symbol: M(c)
     schedules-component: mochitest-chrome
     loopback-video: true
-    e10s: false
+    run-without-variant: false
     variants:
         - 1proc
         - socketprocess_networking+1proc
@@ -789,9 +789,7 @@ mochitest-valgrind:
     loopback-video: true
     chunks: 40
     max-run-time: 14400
-    # We could re-enable e10s later.
-    # There's no intrinsic reason not to use it.
-    e10s: false
+    run-without-variant: false
     variants: ["1proc"]
     allow-software-gl-layers: false
     mozharness:
diff --git a/taskcluster/ci/test/variants.yml b/taskcluster/ci/test/variants.yml
index dc8675c6b576..7bfefdb3bf46 100644
--- a/taskcluster/ci/test/variants.yml
+++ b/taskcluster/ci/test/variants.yml
@@ -4,8 +4,6 @@
     when:
         $eval: '!("android" in task["test-platform"])'
     suffix: "1proc"
-    replace:
-        e10s: false
     merge:
         attributes:
             e10s: false
@@ -28,7 +26,7 @@ aab:
     description: "{description} with aab test_runner"
     contact: agi
     when: &gv_e10s_filter
-        $eval: '"android" in task["test-platform"] && task.e10s in [true, "both"]'
+        $eval: '"android" in task["test-platform"]'
     suffix: "aab"
     # Need to add jdk but there isn't a good way to do that
     # so we just replace the toolchain list
@@ -67,8 +65,6 @@ geckoview-fission:
 fission:
     description: "{description} with fission enabled"
     contact: cpeterson
-    when: &fission_filter
-        $eval: task.e10s in [true, "both"]
     suffix: "fis"
     merge:
         mozharness:
@@ -78,8 +74,6 @@ fission:
 fission-xorigin:
     description: "{description} with cross-origin and fission enabled"
     contact: cpeterson
-    when:
-        <<: *fission_filter
     suffix: "fis-xorig"
     replace:
         e10s: true
diff --git a/taskcluster/gecko_taskgraph/test/test_transforms_test.py b/taskcluster/gecko_taskgraph/test/test_transforms_test.py
index 0c37ec4775c8..a76f8acf1940 100644
--- a/taskcluster/gecko_taskgraph/test/test_transforms_test.py
+++ b/taskcluster/gecko_taskgraph/test/test_transforms_test.py
@@ -85,13 +85,22 @@ def test_split_variants(monkeypatch, run_transform, make_test_task):
     run_split_variants = partial(run_transform, test_transforms.variant.split_variants)
 
     # test no variants
-    input_task = make_test_task()
+    input_task = make_test_task(
+        **{
+            "run-without-variant": True,
+        }
+    )
     tasks = list(run_split_variants(input_task))
     assert len(tasks) == 1
     assert tasks[0] == input_task
 
     # test variants are split into expected tasks
-    input_task["variants"] = ["foo", "bar"]
+    input_task = make_test_task(
+        **{
+            "run-without-variant": True,
+            "variants": ["foo", "bar"],
+        }
+    )
     tasks = list(run_split_variants(input_task))
     assert len(tasks) == 3
     assert tasks[0] == make_test_task()
@@ -104,6 +113,7 @@ def test_split_variants(monkeypatch, run_transform, make_test_task):
     # test composite variants
     input_task = make_test_task(
         **{
+            "run-without-variant": True,
             "variants": ["foo+bar"],
         }
     )
@@ -119,9 +129,10 @@ def test_split_variants(monkeypatch, run_transform, make_test_task):
     # test 'when' filter
     input_task = make_test_task(
         **{
-            "variants": ["foo", "bar", "foo+bar"],
+            "run-without-variant": True,
             # this should cause task to be filtered out of 'bar' and 'foo+bar' variants
             "test-platform": "windows",
+            "variants": ["foo", "bar", "foo+bar"],
         }
     )
     tasks = list(run_split_variants(input_task))
@@ -129,6 +140,17 @@ def test_split_variants(monkeypatch, run_transform, make_test_task):
     assert "unittest_variant" not in tasks[0]["attributes"]
     assert tasks[1]["attributes"]["unittest_variant"] == "foo"
 
+    # test 'run-without-variants=False'
+    input_task = make_test_task(
+        **{
+            "run-without-variant": False,
+            "variants": ["foo"],
+        }
+    )
+    tasks = list(run_split_variants(input_task))
+    assert len(tasks) == 1
+    assert tasks[0]["attributes"]["unittest_variant"] == "foo"
+
 
 @pytest.mark.parametrize(
     "task,expected",
diff --git a/taskcluster/gecko_taskgraph/transforms/test/__init__.py b/taskcluster/gecko_taskgraph/transforms/test/__init__.py
index be3c245e2f1b..d9ef55202aa1 100644
--- a/taskcluster/gecko_taskgraph/transforms/test/__init__.py
+++ b/taskcluster/gecko_taskgraph/transforms/test/__init__.py
@@ -119,13 +119,8 @@ test_description_schema = Schema(
         # The different configurations that should be run against this task, defined
         # in the TEST_VARIANTS object in the variant.py transforms.
         Optional("variants"): [str],
-        # Whether to run this task with e10s.  If false, run
-        # without e10s; if true, run with e10s; if 'both', run one task with and
-        # one task without e10s.  E10s tasks have "-e10s" appended to the test name
-        # and treeherder group.
-        Required("e10s"): optionally_keyed_by(
-            "test-platform", "project", Any(bool, "both")
-        ),
+        # Whether to run this task without any variants applied.
+        Required("run-without-variant"): optionally_keyed_by("test-platform", bool),
         # Whether the task should run with WebRender enabled or not.
         Optional("webrender"): bool,
         Optional("webrender-run-on-projects"): optionally_keyed_by(
@@ -346,7 +341,6 @@ def set_defaults(config, tasks):
         else:
             task.setdefault("webrender", False)
 
-        task.setdefault("e10s", True)
         task.setdefault("try-name", task["test-name"])
         task.setdefault("os-groups", [])
         task.setdefault("run-as-administrator", False)
@@ -363,6 +357,7 @@ def set_defaults(config, tasks):
         task.setdefault("docker-image", {"in-tree": "ubuntu1804-test"})
         task.setdefault("checkout", False)
         task.setdefault("require-signed-extensions", False)
+        task.setdefault("run-without-variant", True)
         task.setdefault("variants", [])
         task.setdefault("supports-artifact-builds", True)
 
@@ -379,16 +374,21 @@ transforms.add_validate(test_description_schema)
 
 @transforms.add
 def resolve_keys(config, tasks):
+    keys = (
+        "require-signed-extensions",
+        "run-without-variant",
+    )
     for task in tasks:
-        resolve_keyed_by(
-            task,
-            "require-signed-extensions",
-            item_name=task["test-name"],
-            enforce_single_match=False,
-            **{
-                "release-type": config.params["release_type"],
-            },
-        )
+        for key in keys:
+            resolve_keyed_by(
+                task,
+                key,
+                item_name=task["test-name"],
+                enforce_single_match=False,
+                **{
+                    "release-type": config.params["release_type"],
+                },
+            )
         yield task
 
 
@@ -443,7 +443,7 @@ def make_job_description(config, tasks):
             label += suffix
             try_name += suffix
 
-        if task["e10s"]:
+        if "1proc" not in attributes.get("unittest_variant", ""):
             label += "-e10s"
 
         if task["chunks"] > 1:
diff --git a/taskcluster/gecko_taskgraph/transforms/test/other.py b/taskcluster/gecko_taskgraph/transforms/test/other.py
index 783d11e4ebf2..ea530a64357e 100644
--- a/taskcluster/gecko_taskgraph/transforms/test/other.py
+++ b/taskcluster/gecko_taskgraph/transforms/test/other.py
@@ -263,7 +263,6 @@ def handle_keyed_by(config, tasks):
         "max-run-time",
         "chunks",
         "suite",
-        "e10s",
         "run-on-projects",
         "os-groups",
         "run-as-administrator",
@@ -760,10 +759,6 @@ def set_e10s_attributes(config, tasks):
             yield task
             continue
 
-        if not task["e10s"]:
-            continue
-
-        task["e10s"] = True
         task["attributes"]["e10s"] = True
         yield task
 
diff --git a/taskcluster/gecko_taskgraph/transforms/test/variant.py b/taskcluster/gecko_taskgraph/transforms/test/variant.py
index b5f04527048d..59af574d3760 100644
--- a/taskcluster/gecko_taskgraph/transforms/test/variant.py
+++ b/taskcluster/gecko_taskgraph/transforms/test/variant.py
@@ -75,7 +75,8 @@ def split_variants(config, tasks):
     for task in tasks:
         variants = task.pop("variants", [])
 
-        yield copy.deepcopy(task)
+        if task.pop("run-without-variant"):
+            yield copy.deepcopy(task)
 
         for name in variants:
             # Apply composite variants (joined by '+') in order.