Please see jsfiddle attached http://jsfiddle.net/HB7LU/13213/.
You need to target the accountIds
by using dot notation.
HTML
<div ng-controller="MyCtrl">
<select>
<option ng-repeat="item in items.accountIds">{{item}}</option>
</select>
</div>
JS/Angular
var myApp = angular.module('myApp', []);
function MyCtrl($scope) {
$scope.items = {
"id": 1,
"firstName": "John1",
"lastName": "Doe1",
"accountIds": [12345, 12346, 12347],
"recipients": [{
"accountNumber": 22222,
"firstName": "Mary1",
"lastName": "Jane1"
}, {
"accountNumber": 33333,
"firstName": "Mary2",
"lastName": "Jane2"
}]
}
}