Prepare the bread: Slice the stale bread into thin, even slices. Lay them in a single layer on a baking sheet.
Dry the bread: For a no-oven method, leave the bread slices out in a dry area overnight until completely hard. For a quicker option, preheat the oven to 250°F. Bake the slices for 30 minutes, flip, and bake another 30 minutes. Turn the oven off and let the bread sit inside for an additional 30 minutes. Remove and cool completely.
Break into pieces: Once fully dry and cool, break the bread slices into smaller pieces with your hands.
Process into crumbs: Working in batches, add half the bread pieces to a food processor and process for about 2 minutes. Sift the crumbs to catch any large pieces and reprocess as needed. Repeat with remaining bread. This creates plain bread crumbs.
Season the crumbs: Return all crumbs to the food processor. Add Italian seasoning, dried parsley, onion powder, and garlic powder. Pulse briefly (no more than 2–3 seconds) just until combined.
Use or store: Your homemade Italian bread crumbs are ready to use or store for later.