diff --git a/Source/Core/VideoBackends/Software/Tev.cpp b/Source/Core/VideoBackends/Software/Tev.cpp
index be6f14d610..3c932b9566 100644
--- a/Source/Core/VideoBackends/Software/Tev.cpp
+++ b/Source/Core/VideoBackends/Software/Tev.cpp
@@ -838,8 +838,10 @@ void Tev::Draw()
     EfbInterface::IncPerfCounterQuadCount(PQ_ZCOMP_OUTPUT);
   }
 
-  BoundingBox::Update(static_cast<u16>(Position[0]), static_cast<u16>(Position[0]),
-                      static_cast<u16>(Position[1]), static_cast<u16>(Position[1]));
+  // The GC/Wii GPU rasterizes in 2x2 pixel groups, so bounding box values will be rounded to the
+  // extents of these groups, rather than the exact pixel.
+  BoundingBox::Update(static_cast<u16>(Position[0] & ~1), static_cast<u16>(Position[0] | 1),
+                      static_cast<u16>(Position[1] & ~1), static_cast<u16>(Position[1] | 1));
 
 #if ALLOW_TEV_DUMPS
   if (g_ActiveConfig.bDumpTevStages)
diff --git a/Source/Core/VideoCommon/PixelShaderGen.cpp b/Source/Core/VideoCommon/PixelShaderGen.cpp
index a2bc73257e..16fb7766e9 100644
--- a/Source/Core/VideoCommon/PixelShaderGen.cpp
+++ b/Source/Core/VideoCommon/PixelShaderGen.cpp
@@ -492,19 +492,30 @@ void UpdateBoundingBox(float2 rawpos) {{
   // such that width = right - left + 1. This has been verified on hardware.
   int2 pos = iround(rawpos * cefbscale + offset);
 
+  // The GC/Wii GPU rasterizes in 2x2 pixel groups, so bounding box values will be rounded to the
+  // extents of these groups, rather than the exact pixel.
+#ifdef API_OPENGL
+  // Need to flip the operands for Y on OpenGL because of lower-left origin.
+  int2 pos_tl = int2(pos.x & ~1, pos.y | 1);
+  int2 pos_br = int2(pos.x | 1, pos.y & ~1);
+#else
+  int2 pos_tl = pos & ~1;
+  int2 pos_br = pos | 1;
+#endif
+
 #ifdef SUPPORTS_SUBGROUP_REDUCTION
   if (CAN_USE_SUBGROUP_REDUCTION) {{
-    int2 min_pos = IS_HELPER_INVOCATION ? int2(2147483647, 2147483647) : pos;
-    int2 max_pos = IS_HELPER_INVOCATION ? int2(-2147483648, -2147483648) : pos;
+    int2 min_pos = IS_HELPER_INVOCATION ? int2(2147483647, 2147483647) : pos_tl;
+    int2 max_pos = IS_HELPER_INVOCATION ? int2(-2147483648, -2147483648) : pos_br;
     SUBGROUP_MIN(min_pos);
     SUBGROUP_MAX(max_pos);
     if (IS_FIRST_ACTIVE_INVOCATION)
       UpdateBoundingBoxBuffer(min_pos, max_pos);
   }} else {{
-    UpdateBoundingBoxBuffer(pos, pos);
+    UpdateBoundingBoxBuffer(pos_tl, pos_br);
   }}
 #else
-  UpdateBoundingBoxBuffer(pos, pos);
+  UpdateBoundingBoxBuffer(pos_tl, pos_br);
 #endif
 }}
 
diff --git a/Source/Core/VideoCommon/RenderBase.cpp b/Source/Core/VideoCommon/RenderBase.cpp
index 0ff5b52902..f93d498fc6 100644
--- a/Source/Core/VideoCommon/RenderBase.cpp
+++ b/Source/Core/VideoCommon/RenderBase.cpp
@@ -187,18 +187,7 @@ void Renderer::ReinterpretPixelData(EFBReinterpretType convtype)
 
 u16 Renderer::BBoxRead(int index)
 {
-  u16 value = BBoxReadImpl(index);
-
-  // The GC/Wii GPU rasterizes in 2x2 pixel groups, so bounding box values will be rounded to the
-  // extents of these groups, rather than the exact pixel.
-  // This would have been handled in the pixel shader, but all attempts to do so did not work on
-  // OpenGL/NVIDIA, due to presumably mystical driver behavior with atomics.
-  if (index == 0 || index == 2)
-    value &= ~1;
-  else
-    value |= 1;
-
-  return value;
+  return BBoxReadImpl(index);
 }
 
 void Renderer::BBoxWrite(int index, u16 value)