diff --git a/core/processor/src/main/java/io/quarkus/annotation/processor/ExtensionAnnotationProcessor.java b/core/processor/src/main/java/io/quarkus/annotation/processor/ExtensionAnnotationProcessor.java
index a5baebfb8d53e..ef5ac7345a216 100644
--- a/core/processor/src/main/java/io/quarkus/annotation/processor/ExtensionAnnotationProcessor.java
+++ b/core/processor/src/main/java/io/quarkus/annotation/processor/ExtensionAnnotationProcessor.java
@@ -1,5 +1,6 @@
 package io.quarkus.annotation.processor;
 
+import static io.quarkus.annotation.processor.Constants.ANNOTATION_CONFIG_GROUP;
 import static io.quarkus.annotation.processor.Constants.ANNOTATION_CONFIG_MAPPING;
 import static javax.lang.model.util.ElementFilter.constructorsIn;
 import static javax.lang.model.util.ElementFilter.fieldsIn;
@@ -27,6 +28,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.Set;
 import java.util.TreeSet;
@@ -545,11 +547,55 @@ private void processMethodConfigItem(ExecutableElement method, Properties javado
 
     private void processMethodConfigMapping(ExecutableElement method, Properties javadocProps, String className) {
         if (method.getModifiers().contains(Modifier.ABSTRACT)) {
-            final String docComment = getRequiredJavadoc(method);
+            // Skip toString method, because mappings can include it and generate it
+            if (method.getSimpleName().contentEquals("toString") && method.getParameters().size() == 0) {
+                return;
+            }
+
+            String docComment = getRequiredJavadoc(method);
             javadocProps.put(className + Constants.DOT + method.getSimpleName().toString(), docComment);
+
+            // Find groups without annotation
+            TypeMirror returnType = method.getReturnType();
+            if (TypeKind.DECLARED.equals(returnType.getKind())) {
+                DeclaredType declaredType = (DeclaredType) returnType;
+                if (!isAnnotationPresent(declaredType.asElement(), ANNOTATION_CONFIG_GROUP)) {
+                    TypeElement type = unwrapConfigGroup(returnType);
+                    if (type != null && ElementKind.INTERFACE.equals(type.getKind())) {
+                        recordMappingJavadoc(type);
+                        configDocItemScanner.addConfigGroups(type);
+                    }
+                }
+            }
         }
     }
 
+    private TypeElement unwrapConfigGroup(TypeMirror typeMirror) {
+        if (typeMirror == null) {
+            return null;
+        }
+
+        DeclaredType declaredType = (DeclaredType) typeMirror;
+        String name = declaredType.asElement().toString();
+        List<? extends TypeMirror> typeArguments = declaredType.getTypeArguments();
+        if (typeArguments.size() == 0) {
+            if (!name.startsWith("java.")) {
+                return (TypeElement) declaredType.asElement();
+            }
+        } else if (typeArguments.size() == 1) {
+            if (name.equals(Optional.class.getName()) ||
+                    name.equals(List.class.getName()) ||
+                    name.equals(Set.class.getName())) {
+                return unwrapConfigGroup(typeArguments.get(0));
+            }
+        } else if (typeArguments.size() == 2) {
+            if (name.equals(Map.class.getName())) {
+                return unwrapConfigGroup(typeArguments.get(1));
+            }
+        }
+        return null;
+    }
+
     private void processConfigGroup(RoundEnvironment roundEnv, TypeElement annotation) {
         final Set<String> groupClassNames = new HashSet<>();
         for (TypeElement i : typesIn(roundEnv.getElementsAnnotatedWith(annotation))) {
diff --git a/core/processor/src/main/java/io/quarkus/annotation/processor/generate_doc/ConfigDocItemFinder.java b/core/processor/src/main/java/io/quarkus/annotation/processor/generate_doc/ConfigDocItemFinder.java
index 7cf05a5099026..39b569f7943a2 100644
--- a/core/processor/src/main/java/io/quarkus/annotation/processor/generate_doc/ConfigDocItemFinder.java
+++ b/core/processor/src/main/java/io/quarkus/annotation/processor/generate_doc/ConfigDocItemFinder.java
@@ -271,7 +271,7 @@ private List<ConfigDocItem> recursivelyFindConfigItems(Element element, String r
                     if (!typeArguments.isEmpty()) {
                         // FIXME: this is super dodgy: we should check the type!!
                         if (typeArguments.size() == 2) {
-                            type = typeArguments.get(1).toString();
+                            type = getType(typeArguments.get(1));
                             if (isConfigGroup(type)) {
                                 name += String.format(NAMED_MAP_CONFIG_ITEM_FORMAT, configDocMapKey);
                                 List<ConfigDocItem> groupConfigItems = readConfigGroupItems(configPhase, rootName, name, type,
@@ -354,8 +354,6 @@ private List<ConfigDocItem> recursivelyFindConfigItems(Element element, String r
                     }
                 }
 
-                final String configDescription = javaDocParser.parseConfigDescription(rawJavaDoc);
-
                 configDocKey.setKey(name);
                 configDocKey.setType(type);
                 configDocKey.setList(list);
@@ -365,7 +363,7 @@ private List<ConfigDocItem> recursivelyFindConfigItems(Element element, String r
                 configDocKey.setConfigPhase(configPhase);
                 configDocKey.setDefaultValue(defaultValue);
                 configDocKey.setDocMapKey(configDocMapKey);
-                configDocKey.setConfigDoc(configDescription);
+                configDocKey.setConfigDoc(javaDocParser.parseConfigDescription(rawJavaDoc));
                 configDocKey.setAcceptedValues(acceptedValues);
                 configDocKey.setJavaDocSiteLink(getJavaDocSiteLink(type));
                 ConfigDocItem configDocItem = new ConfigDocItem();
@@ -413,6 +411,11 @@ private boolean shouldProcessElement(final Element enclosedElement) {
 
         // A ConfigMapping method
         if (enclosedElement.getKind().equals(ElementKind.METHOD)) {
+            ExecutableElement method = (ExecutableElement) enclosedElement;
+            // Skip toString method, because mappings can include it and generate it
+            if (method.getSimpleName().contentEquals("toString") && method.getParameters().size() == 0) {
+                return false;
+            }
             Element enclosingElement = enclosedElement.getEnclosingElement();
             return enclosingElement.getModifiers().contains(ABSTRACT) && enclosedElement.getModifiers().contains(ABSTRACT);
         }
@@ -438,7 +441,7 @@ private String simpleTypeToString(TypeMirror typeMirror) {
             return simpleTypeToString(typeArguments.get(0));
         }
 
-        return typeMirror.toString();
+        return getType(typeMirror);
     }
 
     private List<String> extractEnumValues(TypeMirror realTypeMirror, boolean useHyphenatedEnumValue, String javaDocKey) {