Set initial vuetify v-select value

I believe there are two issues with your set up. Firstly, the initial value should be one of the options in select, i.e., you should have people include your defaultSelected; Secondly your object needs to contain a value field, see v-select props. Otherwise you need to specify item-value prop; See a working example here.

<v-select
  item-text="name"
  item-value="last"
  v-model="defaultSelected"
  :items="people"
>

Vue.use(Vuetify);

 const vm = new Vue({
  el: "#app",
  data: {
    defaultSelected: {
      name: "John",
      last: "Doe"
    },
    people: [
      {
        name: "John",
        last: "Doe"
      },
      {
        name: "Harry",
        last: "Potter"
      },
      {
        name: "George",
        last: "Bush"
      }
    ]
  }
});