It’s commonplace for drafters to use the phrase action or proceeding. Consider the following extract from a jurisdiction provision:
Any party bringing against another party any legal action or proceeding (including any tort claim) arising out of this agreement may bring that action or proceeding in the United States District Court for the Eastern District of Pennsylvania or in any court of the Commonwealth of Pennsylvania sitting in Philadelphia, and each party submits to the nonexclusive jurisdiction of those courts for purposes of any such action or proceeding.
But because proceeding is broader than action, I recommend that instead of action or proceeding you use only proceeding.
Here’s how Black’s Law Dictionary defines proceeding:
proceeding. 1. The regular and orderly progression of a lawsuit, including all acts and events between the time of commencement and the entry of judgment. 2. Any procedural means for seeking redress from a tribunal or agency. 3. An act or step that is part of a larger action. 4. The business conducted by a court or other official body; a hearing. 5. Bankruptcy. A particular dispute or matter arising within a pending case—as opposed to the case as a whole.
Quoting an 1899 source, Black’s goes on to note that proceeding “is more comprehensive than the word ‘action,’ but it may include in its general sense all the steps taken or measures adopted in the prosecution or defense of an action, including the pleadings and judgment.”
In the same vein, here’s what 1A Corpus Juris Secundum Actions § 22 has to say (footnotes omitted):
The term “proceeding” is broader than the word “action.” As ordinarily used, it is broad enough to include all methods of invoking the action of courts and any and all of the steps or measures adopted or taken, or required to be taken, in the prosecution or defense of an action, and is generally applicable to any step taken to obtain the interposition or action of a court. It includes actions and special proceedings before judicial tribunals as well as proceedings pending before quasi-judicial officers and boards, and describes the entire course of an action at law or suit in equity from the filing of the complaint until the entry of final judgment, except, according to some courts, for the pleadings.
So it’s safe to say that in the interest of concision you should use proceeding instead of action or proceeding. (This is contrary to the advice of at least one other book on drafting.)