Can you use special attacks for opportunity attacks?

Question

Can you use a Disarm, Shove or Grapple as your OA? I see no restrictions against it. Am I missing something?

Answer 1

The key here is whether the "special attack" requires the attack action or just a melee or weapon attack. An opportunity attack is a melee attack. It is not an attack action. Therefore, special attacks which require an attack action cannot replace it, whereas special attacks which require only a melee attack can.

---

No for Grapple and Shove

From Sage Advice:

Grappling/shoving are part of the Attack action (PH, 195). Take the Ready action to grapple/shove outside your turn.

---

Yes for Disarming Attack (the fighter maneuver)

Disarming Attack:

When you hit a creature with a weapon attack, you can expend one superiority die to attempt to disarm the target. (PHB 74)

Opportunity Attack:

you use your reaction to make one melee attack against the provoking creature. (PHB 195)

Melee Attacks

A melee attack typically uses a handheld weapon (ibid)

I think that it's fairly clear that an opportunity attack is a weapon attack, and can therefore become a disarming attack if the fighter expends a superiority die.

---

Yes for the Optional Disarm Rule (note that there is no disarm rule in the PHB)

Disarm Contest:

A creature can use a weapon attack to knock a weapon or other item from a target's grasp. (DMG 271)

As above, it only requires a weapon attack, not an attack action. However, you will need to ask your DM (if you are not the DM) as to whether they are using this optional rule.

Answer 2

Yes, no and no.

A Disarming Attack requires a Battlemaster manoeuvre and a weapon attack that hits so the Opportunity attack qualifies.

Grapple says "... use the Attack action ..." and Shoving says "Using the Attack action ..."; an opportunity attack uses your reaction, not your action and specifically not an Attack action.