Sometimes the Reward for a Research Task, is an "Encounter". However, the Research Task doesn't tell you which Pokémon you will Encounter when you complete it. This page should help you to match up which Pokémon may be the Encounter for which Research Tasks.
Available As Raid Boss Only
Available As EX Raid Boss Only
May combine one from each section.
When spinning a PokéStop you get a "Field Research" that may have and Encounter as a Reward. And the Pokémon encountered for a specific Field Research Task may change from time to time. This section allows you to see what Tasks match up with which Encounters, and if you click on the Pokémon, it will show you a CP to IV reference chart.
Look up by:TaskEncounter
Put the Tasks in the first column, then show all the Encounters for that task.
Put the potential Encounters in the first column, then show all the Tasks that can give that Encounter.
Standard Research Tasks
This is a set of Research Tasks and Encounters that don't change much.