diff --git a/lib/edit-site-page.php b/lib/edit-site-page.php
index abb7ced260c0b6..5d7df87db07281 100644
--- a/lib/edit-site-page.php
+++ b/lib/edit-site-page.php
@@ -152,8 +152,7 @@ function gutenberg_edit_site_init( $hook ) {
 			continue;
 		}
 
-		$template_hierarchy = array_merge( get_template_hierachy( $template_type ), get_template_hierachy( 'index' ) );
-		$current_template   = gutenberg_find_template_post_and_parts( $template_hierarchy );
+		$current_template = gutenberg_find_template_post_and_parts( $template_type );
 		if ( isset( $current_template ) ) {
 			$template_ids[ $current_template['template_post']->post_name ] = $current_template['template_post']->ID;
 			$template_part_ids = $template_part_ids + $current_template['template_part_ids'];
diff --git a/lib/template-loader.php b/lib/template-loader.php
index 52bc9bb8637a57..c0be22bc759571 100644
--- a/lib/template-loader.php
+++ b/lib/template-loader.php
@@ -93,7 +93,7 @@ function get_template_hierachy( $template_type ) {
 function gutenberg_override_query_template( $template, $type, array $templates = array() ) {
 	global $_wp_current_template_id, $_wp_current_template_content;
 
-	$current_template = gutenberg_find_template_post_and_parts( $templates );
+	$current_template = gutenberg_find_template_post_and_parts( basename( $template, '.php' ), $templates );
 
 	if ( $current_template ) {
 		$_wp_current_template_id      = $current_template['template_post']->ID;
@@ -191,19 +191,30 @@ function create_auto_draft_for_template_part_block( $block ) {
 }
 
 /**
- * Return the correct 'wp_template' post and template part IDs for the current template hierarchy.
+ * Return the correct 'wp_template' post and template part IDs for the current template.
  *
- * @param string[] $template_hierarchy The current template hierarchy, ordered by priority.
+ * Accepts an optional $template_hierarchy argument as a hint.
+ *
+ * @param string   $template_type      The current template type.
+ * @param string[] $template_hierarchy (optional) The current template hierarchy, ordered by priority.
  * @return null|array {
  *  @type WP_Post|null template_post A template post object, or null if none could be found.
  *  @type int[] A list of template parts IDs for the template.
  * }
  */
-function gutenberg_find_template_post_and_parts( $template_hierarchy ) {
-	if ( ! $template_hierarchy ) {
+function gutenberg_find_template_post_and_parts( $template_type, $template_hierarchy = array() ) {
+	if ( ! $template_type ) {
 		return null;
 	}
 
+	if ( empty( $template_hierarchy ) ) {
+		if ( 'index' === $template_type ) {
+			$template_hierarchy = get_template_hierachy( 'index' );
+		} else {
+			$template_hierarchy = array_merge( get_template_hierachy( $template_type ), get_template_hierachy( 'index' ) );
+		}
+	}
+
 	$slugs = array_map(
 		'gutenberg_strip_php_suffix',
 		$template_hierarchy
diff --git a/lib/templates.php b/lib/templates.php
index 95382cdc16fc56..9336cf44717cfe 100644
--- a/lib/templates.php
+++ b/lib/templates.php
@@ -155,3 +155,51 @@ function gutenberg_render_template_list_table_column( $column_name, $post_id ) {
 	echo esc_html( $post->post_name );
 }
 add_action( 'manage_wp_template_posts_custom_column', 'gutenberg_render_template_list_table_column', 10, 2 );
+
+/**
+ * Filter for adding a `resolved` parameter to `wp_template` queries.
+ *
+ * @param array $query_params The query parameters.
+ * @return array Filtered $query_params.
+ */
+function filter_rest_wp_template_collection_params( $query_params ) {
+	$query_params += array(
+		'resolved' => array(
+			'description' => __( 'Whether to filter for resolved templates', 'gutenberg' ),
+			'type'        => 'boolean',
+		),
+	);
+	return $query_params;
+}
+apply_filters( 'rest_wp_template_collection_params', 'filter_rest_wp_template_collection_params', 99, 1 );
+
+/**
+ * Filter for supporting the `resolved` parameter in `wp_template` queries.
+ *
+ * @param array           $args    The query arguments.
+ * @param WP_REST_Request $request The request object.
+ * @return array Filtered $args.
+ */
+function filter_rest_wp_template_query( $args, $request ) {
+	if ( $request['resolved'] ) {
+		$template_ids   = array( 0 ); // Return nothing by default (the 0 is needed for `post__in`).
+		$template_types = $request['slug'] ? array( $request['slug'] ) : get_template_types();
+
+		foreach ( $template_types as $template_type ) {
+			// Skip 'embed' for now because it is not a regular template type.
+			// Skip 'index' because it's a fallback that we handle differently.
+			if ( in_array( $template_type, array( 'embed', 'index' ), true ) ) {
+				continue;
+			}
+
+			$current_template = gutenberg_find_template_post_and_parts( $template_type );
+			if ( isset( $current_template ) ) {
+				$template_ids[ $current_template['template_post']->post_name ] = $current_template['template_post']->ID;
+			}
+		}
+		$args['post__in'] = array_values( $template_ids );
+	}
+
+	return $args;
+}
+add_filter( 'rest_wp_template_query', 'filter_rest_wp_template_query', 99, 2 );