<select class="ui search dropdown" ng-model="vm.empresa" ng-options="item.id as item.label for item in vm.collectionData.items track by item.id" required >
<option value="">Selecione uma Empresa</option>
</select>
How do I leave the first item already selected by default?
Make a ng-init to select the first element:
<select class="ui search dropdown" ng-init="vm.empresa = vm.collectionData.items[0]" ng-model="vm.empresa" ng-options="item.id as item.label for item in vm.collectionData.items track by item.id" required >
<option value="">Selecione uma Empresa</option>
</select>
so your model will receive the first item in the list.