I recommend using a Computed.property which monitors the models that are changing and combines them into the array you need in your template.
When modelA or modelB changes your computed property will update with those results.
myList: Ember.computed('modelA', 'modelB', function() {
let combinedModels = [];
this.get('modelA').forEach( item => {
// pull out what you need from each model item
combinedModels.push(item);
});
this.get('modelB').forEach( item => {
// pull out what you need from each model item
combinedModels.push(item);
});
return combinedModels;
});