diff --git a/sdk/formrecognizer/Azure.AI.FormRecognizer/CHANGELOG.md b/sdk/formrecognizer/Azure.AI.FormRecognizer/CHANGELOG.md
index 6dab78df2e67..3023486415f1 100644
--- a/sdk/formrecognizer/Azure.AI.FormRecognizer/CHANGELOG.md
+++ b/sdk/formrecognizer/Azure.AI.FormRecognizer/CHANGELOG.md
@@ -5,6 +5,7 @@
 - Renamed the model `Appearance` to `TextAppearance`.
 - Renamed the model `Style` to `TextStyle`.
 - Renamed the extensible enum `TextStyle` to `TextStyleName`.
+- Changed object type for property `Pages` under `RecognizeContentOptions` from `IEnumerable` to `IList`.
 
 ## 3.1.0-beta.1 (2020-11-23)
 
diff --git a/sdk/formrecognizer/Azure.AI.FormRecognizer/api/Azure.AI.FormRecognizer.netstandard2.0.cs b/sdk/formrecognizer/Azure.AI.FormRecognizer/api/Azure.AI.FormRecognizer.netstandard2.0.cs
index 1efa3a039cf7..d0e5240880a3 100644
--- a/sdk/formrecognizer/Azure.AI.FormRecognizer/api/Azure.AI.FormRecognizer.netstandard2.0.cs
+++ b/sdk/formrecognizer/Azure.AI.FormRecognizer/api/Azure.AI.FormRecognizer.netstandard2.0.cs
@@ -70,7 +70,7 @@ public partial class RecognizeContentOptions
         public RecognizeContentOptions() { }
         public Azure.AI.FormRecognizer.FormContentType? ContentType { get { throw null; } set { } }
         public string Language { get { throw null; } set { } }
-        public System.Collections.Generic.IEnumerable<string> Pages { get { throw null; } set { } }
+        public System.Collections.Generic.IList<string> Pages { get { throw null; } }
     }
     public partial class RecognizeCustomFormsOptions
     {
diff --git a/sdk/formrecognizer/Azure.AI.FormRecognizer/src/FormRecognizerClient.cs b/sdk/formrecognizer/Azure.AI.FormRecognizer/src/FormRecognizerClient.cs
index 5e022b31c590..4e1dc818c9ad 100644
--- a/sdk/formrecognizer/Azure.AI.FormRecognizer/src/FormRecognizerClient.cs
+++ b/sdk/formrecognizer/Azure.AI.FormRecognizer/src/FormRecognizerClient.cs
@@ -142,7 +142,7 @@ public virtual RecognizeContentOperation StartRecognizeContent(Stream form, Reco
                     formContentType.ConvertToContentType1(),
                     form,
                     recognizeContentOptions.Language == null ? (Language?)null : recognizeContentOptions.Language,
-                    recognizeContentOptions.Pages,
+                    recognizeContentOptions.Pages.Count == 0 ? null : recognizeContentOptions.Pages,
                     cancellationToken);
                 string location = ClientCommon.GetResponseHeader(response.Headers, Constants.OperationLocationHeader);
 
@@ -181,7 +181,7 @@ public virtual async Task<RecognizeContentOperation> StartRecognizeContentAsync(
                     formContentType.ConvertToContentType1(),
                     form,
                     recognizeContentOptions.Language == null ? (Language?)null : recognizeContentOptions.Language,
-                    recognizeContentOptions.Pages,
+                    recognizeContentOptions.Pages.Count == 0 ? null : recognizeContentOptions.Pages,
                     cancellationToken).ConfigureAwait(false);
                 string location = ClientCommon.GetResponseHeader(response.Headers, Constants.OperationLocationHeader);
 
@@ -217,7 +217,7 @@ public virtual RecognizeContentOperation StartRecognizeContentFromUri(Uri formUr
                 SourcePath sourcePath = new SourcePath() { Source = formUri.AbsoluteUri };
                 Response response = ServiceClient.AnalyzeLayoutAsync(
                     recognizeContentOptions.Language == null ? (Language?)null : recognizeContentOptions.Language,
-                    recognizeContentOptions.Pages,
+                    recognizeContentOptions.Pages.Count == 0 ? null : recognizeContentOptions.Pages,
                     sourcePath,
                     cancellationToken);
                 string location = ClientCommon.GetResponseHeader(response.Headers, Constants.OperationLocationHeader);
@@ -254,7 +254,7 @@ public virtual async Task<RecognizeContentOperation> StartRecognizeContentFromUr
                 SourcePath sourcePath = new SourcePath() { Source = formUri.AbsoluteUri };
                 Response response = await ServiceClient.AnalyzeLayoutAsyncAsync(
                     recognizeContentOptions.Language == null ? (Language?)null : recognizeContentOptions.Language,
-                    recognizeContentOptions.Pages,
+                    recognizeContentOptions.Pages.Count == 0 ? null : recognizeContentOptions.Pages,
                     sourcePath,
                     cancellationToken).ConfigureAwait(false);
                 string location = ClientCommon.GetResponseHeader(response.Headers, Constants.OperationLocationHeader);
diff --git a/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeContentOptions.cs b/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeContentOptions.cs
index 8ff0abf132fd..eaf0b9072f96 100644
--- a/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeContentOptions.cs
+++ b/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeContentOptions.cs
@@ -38,10 +38,16 @@ public RecognizeContentOptions()
         public string Language { get; set; }
 
         /// <summary>
-        /// Custom page numbers for multi-page documents(PDF/TIFF). Input the number of the
-        /// pages you want to get OCR result. For a range of pages, use a hyphen.
-        /// Separate each page or range with a comma.
+        /// <para>
+        /// Custom page numbers for multi-page documents(PDF/TIFF). Input the page numbers
+        /// and/or ranges of pages you want to get in the result. For a range of pages, use a hyphen, like
+        /// `Pages = { "1-3", "5-6" }`. Separate each page number or range with a comma.
+        /// </para>
+        /// <para>
+        /// Although this collection cannot be set, it can be modified.
+        /// See <a href="https://docs.microsoft.com/dotnet/csharp/programming-guide/classes-and-structs/object-and-collection-initializers#collection-initializers">collection initializer</a>.
+        /// </para>
         /// </summary>
-        public IEnumerable<string> Pages { get; set; }
+        public IList<string> Pages { get; } = new List<string>();
     }
 }
diff --git a/sdk/formrecognizer/Azure.AI.FormRecognizer/tests/FormRecognizerClient/FormRecognizerClientLiveTests.cs b/sdk/formrecognizer/Azure.AI.FormRecognizer/tests/FormRecognizerClient/FormRecognizerClientLiveTests.cs
index a6744ab80c3c..33b0d0108810 100644
--- a/sdk/formrecognizer/Azure.AI.FormRecognizer/tests/FormRecognizerClient/FormRecognizerClientLiveTests.cs
+++ b/sdk/formrecognizer/Azure.AI.FormRecognizer/tests/FormRecognizerClient/FormRecognizerClientLiveTests.cs
@@ -461,7 +461,7 @@ public async Task StartRecognizeContentWithOnePageArgument(string pages, int exp
             using var stream = FormRecognizerTestEnvironment.CreateStream(TestFile.InvoiceMultipageBlank);
             using (Recording.DisableRequestBodyRecording())
             {
-                operation = await client.StartRecognizeContentAsync(stream, new RecognizeContentOptions() { Pages = new List<string> { pages } });
+                operation = await client.StartRecognizeContentAsync(stream, new RecognizeContentOptions() { Pages =  { pages } });
             }
 
             FormPageCollection formPages = await operation.WaitForCompletionAsync(PollingInterval);
@@ -480,7 +480,7 @@ public async Task StartRecognizeContentWithMultiplePageArgument(string page1, st
             using var stream = FormRecognizerTestEnvironment.CreateStream(TestFile.InvoiceMultipageBlank);
             using (Recording.DisableRequestBodyRecording())
             {
-                operation = await client.StartRecognizeContentAsync(stream, new RecognizeContentOptions() { Pages = new List<string> { page1, page2 } });
+                operation = await client.StartRecognizeContentAsync(stream, new RecognizeContentOptions() { Pages = { page1, page2 } });
             }
 
             FormPageCollection formPages = await operation.WaitForCompletionAsync(PollingInterval);