diff --git a/ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/RequiredPluginsInitializer.java b/ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/RequiredPluginsInitializer.java
index a639647fbba..26931e0a43a 100644
--- a/ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/RequiredPluginsInitializer.java
+++ b/ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/RequiredPluginsInitializer.java
@@ -13,20 +13,33 @@
  *******************************************************************************/
 package org.eclipse.pde.internal.core;
 
+import java.lang.StackWalker.Option;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import org.eclipse.core.resources.IProject;
 import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.ILog;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.jobs.IJobChangeEvent;
 import org.eclipse.core.runtime.jobs.Job;
+import org.eclipse.core.runtime.jobs.JobChangeAdapter;
 import org.eclipse.jdt.core.ClasspathContainerInitializer;
 import org.eclipse.jdt.core.IClasspathContainer;
 import org.eclipse.jdt.core.IJavaProject;
 import org.eclipse.jdt.core.JavaCore;
+import org.eclipse.jdt.core.JavaModelException;
 import org.eclipse.pde.core.plugin.IPluginModelBase;
 
 public class RequiredPluginsInitializer extends ClasspathContainerInitializer {
 
+	private static final AtomicBoolean WARNING_LOGGED = new AtomicBoolean();
+
+	private static final Map<IJavaProject, Job> JOB_MAP = new ConcurrentHashMap<>();
+
 	private static final Job initPDEJob = Job.create(PDECoreMessages.PluginModelManager_InitializingPluginModels,
 			monitor -> {
 				if (!PDECore.getDefault().getModelManager().isInitialized()) {
@@ -34,8 +47,52 @@ public class RequiredPluginsInitializer extends ClasspathContainerInitializer {
 				}
 			});
 
+	private static StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
+
 	@Override
 	public void initialize(IPath containerPath, IJavaProject javaProject) throws CoreException {
+		if (isCalledWhileWorkbenchStartup()) {
+			// See https://github.com/eclipse-pde/eclipse.pde/issues/1481
+			if (WARNING_LOGGED.compareAndSet(false, true)) {
+				ILog.get().warn(
+						"RequiredPluginsInitializer called from within the Application startup thread this will badly impact your IDE performance!", //$NON-NLS-1$
+						new RuntimeException("Called from Application startup thread thread here")); //$NON-NLS-1$
+			}
+			JOB_MAP.compute(javaProject, (jp, oldjob) -> {
+				if (oldjob != null) {
+					oldjob.cancel();
+				}
+				Job job = Job.create(PDECoreMessages.PluginModelManager_InitializingPluginModels, m -> {
+					if (oldjob != null) {
+						try {
+							oldjob.join();
+						} catch (InterruptedException e) {
+						}
+					}
+					setClasspath(jp);
+				});
+				job.addJobChangeListener(new JobChangeAdapter() {
+					@Override
+					public void done(IJobChangeEvent event) {
+						JOB_MAP.remove(jp);
+					}
+				});
+				job.schedule();
+				return job;
+			});
+			return;
+		}
+		Job job = JOB_MAP.get(javaProject);
+		if (job != null) {
+			try {
+				job.join();
+			} catch (InterruptedException e) {
+			}
+		}
+		setClasspath(javaProject);
+	}
+
+	protected void setClasspath(IJavaProject javaProject) throws JavaModelException {
 		IProject project = javaProject.getProject();
 		// The first project to be built may initialize the PDE models, potentially long running, so allow cancellation
 		PluginModelManager manager = PDECore.getDefault().getModelManager();
@@ -85,4 +142,14 @@ public void requestClasspathContainerUpdate(IPath containerPath, IJavaProject pr
 		JavaCore.setClasspathContainer(containerPath, new IJavaProject[] {project}, new IClasspathContainer[] {containerSuggestion}, null);
 	}
 
+	private static boolean isCalledWhileWorkbenchStartup() {
+
+		return walker.walk(frames -> {
+			return frames.anyMatch(sf -> {
+				return "org.eclipse.e4.ui.internal.workbench.E4Workbench".equals(sf.getClassName()) //$NON-NLS-1$
+						&& "createAndRunUI".equals(sf.getMethodName()); //$NON-NLS-1$
+			});
+		});
+	}
+
 }