diff --git a/src/Api/Controllers/GroupsController.cs b/src/Api/Controllers/GroupsController.cs
index 0220cfd5e2..b704602f39 100644
--- a/src/Api/Controllers/GroupsController.cs
+++ b/src/Api/Controllers/GroupsController.cs
@@ -1,7 +1,11 @@
 using Bit.Api.Models.Request;
 using Bit.Api.Models.Response;
+using Bit.Api.Vault.AuthorizationHandlers.Groups;
+using Bit.Core;
 using Bit.Core.Context;
+using Bit.Core.Entities;
 using Bit.Core.Exceptions;
+using Bit.Core.Models.Data;
 using Bit.Core.OrganizationFeatures.Groups.Interfaces;
 using Bit.Core.Repositories;
 using Bit.Core.Services;
@@ -21,6 +25,10 @@ public class GroupsController : Controller
     private readonly ICurrentContext _currentContext;
     private readonly ICreateGroupCommand _createGroupCommand;
     private readonly IUpdateGroupCommand _updateGroupCommand;
+    private readonly IFeatureService _featureService;
+    private readonly IAuthorizationService _authorizationService;
+
+    private bool FlexibleCollectionsIsEnabled => _featureService.IsEnabled(FeatureFlagKeys.FlexibleCollections, _currentContext);
 
     public GroupsController(
         IGroupRepository groupRepository,
@@ -29,7 +37,9 @@ public class GroupsController : Controller
         ICurrentContext currentContext,
         ICreateGroupCommand createGroupCommand,
         IUpdateGroupCommand updateGroupCommand,
-        IDeleteGroupCommand deleteGroupCommand)
+        IDeleteGroupCommand deleteGroupCommand,
+        IFeatureService featureService,
+        IAuthorizationService authorizationService)
     {
         _groupRepository = groupRepository;
         _groupService = groupService;
@@ -38,6 +48,8 @@ public class GroupsController : Controller
         _createGroupCommand = createGroupCommand;
         _updateGroupCommand = updateGroupCommand;
         _deleteGroupCommand = deleteGroupCommand;
+        _featureService = featureService;
+        _authorizationService = authorizationService;
     }
 
     [HttpGet("{id}")]
@@ -65,20 +77,34 @@ public class GroupsController : Controller
     }
 
     [HttpGet("")]
-    public async Task<ListResponseModel<GroupDetailsResponseModel>> Get(string orgId)
+    public async Task<ListResponseModel<GroupDetailsResponseModel>> Get(Guid orgId)
     {
-        var orgIdGuid = new Guid(orgId);
-        var canAccess = await _currentContext.ManageGroups(orgIdGuid) ||
-            await _currentContext.ViewAssignedCollections(orgIdGuid) ||
-            await _currentContext.ViewAllCollections(orgIdGuid) ||
-            await _currentContext.ManageUsers(orgIdGuid);
+        ICollection<Tuple<Group, ICollection<CollectionAccessSelection>>> groups;
 
-        if (!canAccess)
+        if (FlexibleCollectionsIsEnabled)
         {
-            throw new NotFoundException();
+            groups = await _groupRepository.GetManyWithCollectionsByOrganizationIdAsync(orgId);
+            var authorized = (await _authorizationService.AuthorizeAsync(User, groups.Select(g => g.Item1), GroupOperations.Read)).Succeeded;
+            if (!authorized)
+            {
+                throw new NotFoundException();
+            }
+        }
+        else
+        {
+            var canAccess = await _currentContext.ManageGroups(orgId) ||
+                            await _currentContext.ViewAssignedCollections(orgId) ||
+                            await _currentContext.ViewAllCollections(orgId) ||
+                            await _currentContext.ManageUsers(orgId);
+
+            if (!canAccess)
+            {
+                throw new NotFoundException();
+            }
+
+            groups = await _groupRepository.GetManyWithCollectionsByOrganizationIdAsync(orgId);
         }
 
-        var groups = await _groupRepository.GetManyWithCollectionsByOrganizationIdAsync(orgIdGuid);
         var responses = groups.Select(g => new GroupDetailsResponseModel(g.Item1, g.Item2));
         return new ListResponseModel<GroupDetailsResponseModel>(responses);
     }
diff --git a/src/Api/Utilities/ServiceCollectionExtensions.cs b/src/Api/Utilities/ServiceCollectionExtensions.cs
index be6a7a066a..cdf6442af4 100644
--- a/src/Api/Utilities/ServiceCollectionExtensions.cs
+++ b/src/Api/Utilities/ServiceCollectionExtensions.cs
@@ -1,4 +1,6 @@
 using Bit.Api.Vault.AuthorizationHandlers.Collections;
+using Bit.Api.Vault.AuthorizationHandlers.Groups;
+using Bit.Api.Vault.AuthorizationHandlers.OrganizationUsers;
 using Bit.Core.IdentityServer;
 using Bit.Core.Settings;
 using Bit.Core.Utilities;
@@ -121,5 +123,7 @@ public static class ServiceCollectionExtensions
     public static void AddAuthorizationHandlers(this IServiceCollection services)
     {
         services.AddScoped<IAuthorizationHandler, CollectionAuthorizationHandler>();
+        services.AddScoped<IAuthorizationHandler, GroupAuthorizationHandler>();
+        services.AddScoped<IAuthorizationHandler, OrganizationUserAuthorizationHandler>();
     }
 }
diff --git a/src/Api/Vault/AuthorizationHandlers/Groups/GroupAuthorizationHandler.cs b/src/Api/Vault/AuthorizationHandlers/Groups/GroupAuthorizationHandler.cs
new file mode 100644
index 0000000000..31af8ff782
--- /dev/null
+++ b/src/Api/Vault/AuthorizationHandlers/Groups/GroupAuthorizationHandler.cs
@@ -0,0 +1,97 @@
+using Bit.Core;
+using Bit.Core.Context;
+using Bit.Core.Entities;
+using Bit.Core.Enums;
+using Bit.Core.Exceptions;
+using Bit.Core.Services;
+using Bit.Core.Utilities;
+using Microsoft.AspNetCore.Authorization;
+
+namespace Bit.Api.Vault.AuthorizationHandlers.Groups;
+
+/// <summary>
+/// Handles authorization logic for Group objects.
+/// This uses new logic implemented in the Flexible Collections initiative.
+/// </summary>
+public class GroupAuthorizationHandler : BulkAuthorizationHandler<GroupOperationRequirement, Group>
+{
+    private readonly ICurrentContext _currentContext;
+    private readonly IFeatureService _featureService;
+
+    public GroupAuthorizationHandler(
+        ICurrentContext currentContext,
+        IFeatureService featureService)
+    {
+        _currentContext = currentContext;
+        _featureService = featureService;
+    }
+
+    protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context,
+        GroupOperationRequirement requirement, ICollection<Group> resources)
+    {
+        if (!_featureService.IsEnabled(FeatureFlagKeys.FlexibleCollections, _currentContext))
+        {
+            // Flexible collections is OFF, should not be using this handler
+            throw new FeatureUnavailableException("Flexible collections is OFF when it should be ON.");
+        }
+
+        // Establish pattern of authorization handler null checking passed resources
+        if (resources == null)
+        {
+            context.Fail();
+            return;
+        }
+
+        if (!resources.Any())
+        {
+            context.Succeed(requirement);
+            return;
+        }
+
+        if (!_currentContext.UserId.HasValue)
+        {
+            context.Fail();
+            return;
+        }
+
+        var targetOrganizationId = resources.First().OrganizationId;
+
+        // Ensure all target collections belong to the same organization
+        if (resources.Any(tc => tc.OrganizationId != targetOrganizationId))
+        {
+            throw new BadRequestException("Requested groups must belong to the same organization.");
+        }
+
+        // Acting user is not a member of the target organization, fail
+        var org = _currentContext.GetOrganization(targetOrganizationId);
+        if (org == null)
+        {
+            context.Fail();
+            return;
+        }
+
+        switch (requirement)
+        {
+            case not null when requirement == GroupOperations.Read:
+                await CanReadAsync(context, requirement, org);
+                break;
+        }
+    }
+
+    private async Task CanReadAsync(AuthorizationHandlerContext context, GroupOperationRequirement requirement,
+        CurrentContextOrganization org)
+    {
+        if (org.Type is OrganizationUserType.Owner or OrganizationUserType.Admin ||
+            org.Permissions.ManageGroups ||
+            org.Permissions.ManageUsers ||
+            org.Permissions.EditAnyCollection ||
+            org.Permissions.DeleteAnyCollection ||
+            await _currentContext.ProviderUserForOrgAsync(org.Id))
+        {
+            context.Succeed(requirement);
+            return;
+        }
+
+        context.Fail();
+    }
+}
diff --git a/src/Api/Vault/AuthorizationHandlers/Groups/GroupOperations.cs b/src/Api/Vault/AuthorizationHandlers/Groups/GroupOperations.cs
new file mode 100644
index 0000000000..8cac205dda
--- /dev/null
+++ b/src/Api/Vault/AuthorizationHandlers/Groups/GroupOperations.cs
@@ -0,0 +1,10 @@
+using Microsoft.AspNetCore.Authorization.Infrastructure;
+
+namespace Bit.Api.Vault.AuthorizationHandlers.Groups;
+
+public class GroupOperationRequirement : OperationAuthorizationRequirement { }
+
+public static class GroupOperations
+{
+    public static readonly GroupOperationRequirement Read = new() { Name = nameof(Read) };
+}