diff --git a/src/FSharpPlus/Extensions/Dict.fs b/src/FSharpPlus/Extensions/Dict.fs
index e54743052..8d0532f47 100644
--- a/src/FSharpPlus/Extensions/Dict.fs
+++ b/src/FSharpPlus/Extensions/Dict.fs
@@ -46,6 +46,16 @@ module Dict =
     /// <returns>A seq of the values in the dictionary.</returns>
     let values (source: IDictionary<_, _>) = Seq.map (fun (KeyValue(_, v)) -> v) source
 
+    /// <summary>Applies the given function to each key and value pair of the dictionary.</summary>
+    /// <param name="action">The function to apply to each key and value pair of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iter action (source: IDictionary<'Key, 'T>) = for KeyValue(k, v) in source do action k v
+
+    /// <summary>Applies the given function to each value of the dictionary.</summary>
+    /// <param name="action">The function to apply to each value of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iterValues action (source: IDictionary<'Key, 'T>) = for KeyValue(_, v) in source do action v
+
     /// <summary>Maps the given function over each value in the dictionary.</summary>
     /// <param name="mapper">The mapping function.</param>
     /// <param name="source">The input dictionary.</param>
diff --git a/src/FSharpPlus/Extensions/Dictionary.fs b/src/FSharpPlus/Extensions/Dictionary.fs
index c569cf466..3030f0783 100644
--- a/src/FSharpPlus/Extensions/Dictionary.fs
+++ b/src/FSharpPlus/Extensions/Dictionary.fs
@@ -48,6 +48,16 @@ module Dictionary =
     /// <returns>A seq of the values in the dictionary.</returns>
     let values (source: Dictionary<_,_>) = Seq.map (fun (KeyValue(_, v)) -> v) source
 
+    /// <summary>Applies the given function to each key and value pair of the dictionary.</summary>
+    /// <param name="action">The function to apply to each key and value pair of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iter action (source: Dictionary<'Key, 'T>) = for KeyValue(k, v) in source do action k v
+
+    /// <summary>Applies the given function to each value of the dictionary.</summary>
+    /// <param name="action">The function to apply to each value of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iterValues action (source: Dictionary<'Key, 'T>) = for KeyValue(_, v) in source do action v
+
     /// <summary>Maps the given function over each value in the dictionary.</summary>
     /// <param name="mapping">The mapping function.</param>
     /// <param name="source">The input dictionary.</param>
diff --git a/src/FSharpPlus/Extensions/IReadOnlyCollection.fs b/src/FSharpPlus/Extensions/IReadOnlyCollection.fs
index 1a3b5626a..047c4f048 100644
--- a/src/FSharpPlus/Extensions/IReadOnlyCollection.fs
+++ b/src/FSharpPlus/Extensions/IReadOnlyCollection.fs
@@ -11,5 +11,10 @@ module IReadOnlyCollection =
     let ofList  (source: 'T list) = source                :> IReadOnlyCollection<'T>
     let ofSeq   (source: seq<'T>) = source |> Array.ofSeq :> IReadOnlyCollection<'T>
     let map  mapping (source: IReadOnlyCollection<'T>) = Seq.map  mapping source |> Seq.toArray :> IReadOnlyCollection<'U>
-    let iter mapping (source: IReadOnlyCollection<'T>) = Seq.iter mapping source
+    
+    /// <summary>Applies the given function to each element of the collection.</summary>
+    /// <param name="action">The function to apply to elements from the input collection.</param>
+    /// <param name="source">The input collection.</param>
+    let iter action (source: IReadOnlyCollection<'T>) = Seq.iter action source
+
     let isEmpty (source: IReadOnlyCollection<'T>) = source.Count = 0
diff --git a/src/FSharpPlus/Extensions/IReadOnlyDictionary.fs b/src/FSharpPlus/Extensions/IReadOnlyDictionary.fs
index 9414c0c54..20b07caee 100644
--- a/src/FSharpPlus/Extensions/IReadOnlyDictionary.fs
+++ b/src/FSharpPlus/Extensions/IReadOnlyDictionary.fs
@@ -49,6 +49,16 @@ module IReadOnlyDictionary =
     /// <returns>A seq of the values in the read-only dictionary.</returns>
     let values (source: IReadOnlyDictionary<'Key, 'Value>) = Seq.map (fun (KeyValue(_, v)) -> v) source
 
+    /// <summary>Applies the given function to each key and value pair of the read-only dictionary.</summary>
+    /// <param name="action">The function to apply to each key and value pair of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iter action (source: IReadOnlyDictionary<'Key, 'T>) = for KeyValue(k, v) in source do action k v
+
+    /// <summary>Applies the given function to each value of the read-only dictionary.</summary>
+    /// <param name="action">The function to apply to each value of the input dictionary.</param>
+    /// <param name="source">The input dictionary.</param>
+    let iterValues action (source: IReadOnlyDictionary<'Key, 'T>) = for KeyValue(_, v) in source do action v
+
     /// <summary>Maps the given function over each value in the read-only dictionary.</summary>
     /// <param name="mapper">The mapping function.</param>
     /// <param name="source">The input IReadOnlyDictionary.</param>
@@ -106,13 +116,6 @@ module IReadOnlyDictionary =
             dct.Add (k, mapper k v)
         dct :> IReadOnlyDictionary<'Key, 'U>
 
-    /// <summary>Applies the given action over each key and value in the read-only dictionary.</summary>
-    /// <param name="action">The action to apply.</param>
-    /// <param name="source">The input IReadOnlyDictionary.</param>
-    ///
-    /// <returns>The mapped IReadOnlyDictionary.</returns>
-    let iter action (source: IReadOnlyDictionary<'Key, 'T>) = for KeyValue(k, v) in source do action k v
-
 
     /// <summary>Applies a function to each value in a read-only dictionary and then returns
     /// a read-only dictionary of entries <c>v</c> where the applied function returned <c>Some(v)</c>.
diff --git a/src/FSharpPlus/Extensions/IReadOnlyList.fs b/src/FSharpPlus/Extensions/IReadOnlyList.fs
index e4ad6c2c2..a9ae04840 100644
--- a/src/FSharpPlus/Extensions/IReadOnlyList.fs
+++ b/src/FSharpPlus/Extensions/IReadOnlyList.fs
@@ -32,4 +32,7 @@ module IReadOnlyList =
         if 0 <= i && i < source.Count then Some source.[i]
         else None
 
-    let iter mapping (source: IReadOnlyList<'T>) = Seq.iter mapping source
\ No newline at end of file
+    /// <summary>Applies the given function to each element of the collection.</summary>
+    /// <param name="action">The function to apply to elements from the input list.</param>
+    /// <param name="source">The input list.</param>
+    let iter action (source: IReadOnlyList<'T>) = Seq.iter action source
\ No newline at end of file
diff --git a/src/FSharpPlus/Extensions/Map.fs b/src/FSharpPlus/Extensions/Map.fs
index c6d241faf..d6781d45b 100644
--- a/src/FSharpPlus/Extensions/Map.fs
+++ b/src/FSharpPlus/Extensions/Map.fs
@@ -33,6 +33,11 @@ module Map =
     /// </remarks>
     let values (source: Map<'Key, 'T>) = Seq.map (fun (KeyValue(_, v)) -> v) source
 
+    /// <summary>Applies the given function to each value of the Map.</summary>
+    /// <param name="action">The function to apply to each value of the input Map.</param>
+    /// <param name="source">The input Map.</param>
+    let iterValues action (source: Map<'Key, 'T>) = Map.iter (fun _ v -> action v) source
+
     /// <summary>Maps the values of the original Map.</summary>
     /// <remarks>
     /// The core `Map.map` function maps over values too, but it passes both
diff --git a/src/FSharpPlus/Extensions/ResizeArray.fs b/src/FSharpPlus/Extensions/ResizeArray.fs
index 425873748..f321b13e6 100644
--- a/src/FSharpPlus/Extensions/ResizeArray.fs
+++ b/src/FSharpPlus/Extensions/ResizeArray.fs
@@ -21,6 +21,14 @@ module ResizeArray =
         
         ResizeArray (Seq.map mapping source)
 
+    /// <summary>Applies the given function to each element of the collection.</summary>
+    /// <param name="action">The function to apply to elements from the input ResizeArray.</param>
+    /// <param name="source">The input ResizeArray.</param>
+    let iter (action: 'T -> 'U) (source: ResizeArray<'T>) =
+        raiseIfNull (nameof source) source
+        
+        ResizeArray (Seq.map action source)
+
     /// <summary>Applies a ResizeArray of functions to a ResizeArray of values and concatenates them.</summary>
     /// <param name="f">The functions.</param>
     /// <param name="ra">The values.</param>